More slope fixes (aka sorry guys I made another quick SUGOI fix)

Another slopes fix branch!

This branch currently includes a fix for:
* Knuckles gliding into a slope while in 2D mode causes him to try to "climb" on air above them, if the original non-sloped height is higher. Unfortunately he still tries to grab onto places that he can't really climb on, but at least now it's on the slope itself and not in mid-air lol. This issue is encountered in SUGOI's Retro Hill Zone, if you want to check for yourselves.
* Bustable FOF-busting code for both players AND pushables not accounting for slopes
* (Unrelated to slopes): Fix FF_SHATTERBOTTOM FOFs acting like THZ goop when stood on; I added this fix as a bonus because I encountered it in a test map of mine for the bustables fix

(Other fixes may or may not appear here in the near future, I haven't decided yet. Don't wait on me to get in any further fixes before merging, that said)

See merge request !110

Last-minute NiGHTS exiting bugfix

One single-line fix concerning the end of NiGHTS maps. Extremely small, literally zero side effects here, the only reason I'm not committing directly to master (aside from ettiquette) is that I don't have the ability to do so.

* The NiGHTS drone had a single tic of visibility when you hit the goal, which is evident stepping frame by frame through http://gfycat.com/ComplicatedComposedAoudad (the contents of which may or may not make it into 2.2). This is no longer the case.

See merge request !100

DIsable NetPlay on DirectDraw builds

Also disable UPnP support on NONET builds

See merge request !102

Record Attack hotfix

Limit damage from http://mb.srb2.org/showthread.php?t=41847, basically.

Also fixed the message popup background because why not

See merge request !107

Fix Knuckles in 2D mode attempting to latch onto air when gliding into a slope. Now he just attempts to latch onto the slope directly (which I'll fix another time, if I can figure out how)

(fix for SUGOI's Retro Hill Zone)

Cutscene switch fix

Yet another fix for SUGOI, lol: apparently going from a final level's post-cutscene straight to a custom credits cutscene gets the latter stuck forever in the first scene (because the game accidentally stops the cutscene responder from realising the custom credits cutscene is running). This branch of course makes a fix for that.

See merge request !108

Wall collision fixes

Fixes included in this branch:
* A fix for a specific crash encountered in a SUGOI map (sound familiar?) caused by bouncing off a wall adjacent to a slope
* A fix for solid midtextures not accounting for Effect 3/Peg Midtexture properly (https://mb.srb2.org/showthread.php?t=41462)
* A fix for solid midtextures not accounting for texture y offsets properly for non-Lower Unpegged/Peg Midtextured midtextures
* A fix for solid midtextures not accounting for "infinite" repeats (Repeat Midtexture + no repeat count set)
* ~~A fix for Effect 4 on Polyobject First Line making that particular linedef's midtexture solid in addition to making planes visible - this is not wanted if you want a polyobject with both visible planes and full intangibility.~~ Apparently they never did this anyway, don't mind me \o/

See merge request !104

Climbing shit 2 electric boogaloo: an adventure in how much toast hates how the ogl renderer was implemented

Fixed Knuckles being able to climb in space in OpenGL.

Using the last-touched line instead of R_IsPointInSubsector because FLOAT_TO_FIXED is bad in P_ functions

To understand the original problem: look at AjustSegs(void) in hw_bsp.c. It reallocates the vetex_t pointers for lines as POLYVERTEX_T pointers, and of COURSE things are gonna get wacky when you're casting pointers.

This merge request is into master because it's a bug that's IN master and must never reach the public because of how bad it is

See merge request !101

Fix non-player objects having busted step-up/down on slopes

Why the fuck did I make this a player conditional in the first place holy shit

See merge request !103

Allowing the disabling of Match/CTF/Miscellaneous Ringslinger HUD elements

Does what it says on the tin.

Requested by Lat and Speedwagon, selfishly also desired because of Thokker, open and shut. If 2.1.16 is delayed, might as well get some goodwill-raising zero-effort stuff in there.

See merge request !106

RA menu can be opened if the game is modified, but Start can't be selected. (Obvious reason: so scripts to display info can be used easier)
Fixed the stupid background for messages in the Record Attack menu, it was bugging me

The ability to disable weapon rings, as heavily requested by Lat and Speedwagon for their high effort character .wads and selfishly also desired to make thokker less hacky.

* Effect 3 (Peg Midtexture) is now accounted for properly, flipping the collision box position to match the actual rendered position of the midtexture
* Fixed incorrect application of y-offsets for non-lower unpegged midtextures collision boxes; +ve always goes up, -ve always goes down!
* Effect 4 now doesn't make midtextures solid for polyobjects at all - this "conflicted" with First Line having both Effect 4 (visible planes) and Effect 3 (intangible) simultaneously, where we kind of expect the first line's wall to not be made solid. This may be less of a problem in future SRB2 versions, but for now solid midtextures for polyobjects are disabled.

. tmthing can be NULL if called from PTR_SlideTraverse, so we should use slidemo instead

This fixes a crash that occurs in yet ANOTHER SUGOI map, involving bouncy walls next to sloped floors/ceilings

Solved the climbing-on-one-sided-lines problem another way, using the last touched line's attributes.

(After talking to Alam, we can't have floats anywhere near P_ functions, so.)

To understand: look at AjustSegs(void) in hw_bsp.c. It reallocates the vetex_t pointers for lines as POLYVERTEX_T pointers, and of COURSE things are gonna get wacky when you're casting pointers.

I dunno how resilient the FLOAT_TO_FIXED solution is or whether it'll be netgame compatible (yayyy float precision loss) but it's not like our builds are netgame compatible with themselves

* The NiGHTS drone had a single tic of visibility when you hit the goal, which is evident stepping frame by frame through http://gfycat.com/ComplicatedComposedAoudad (the contents of which may or may not make it into 2.2).
* When completing a NiGHTS stage with a non-zero link, the link could flash up in the final few tics before the fade to black. This just checks for player->exiting to make sure it shouldn't be shown.

OpenGL planes fix

This branch removes a specific hack in the OpenGL code for detecting if a plane is for the floor or ceiling of a sector. This it turns out fixes ceiling slopes in Boinciel's SUGOI map going missing. Though, It doesn't fix that other glitch with one FOF (must be unrelated).

If you want to test these fixes out properly, make sure working in-level sectors, FOFs AND also polyobjects all still work fine, sloped or not.

See merge request !97

Fof slope crash fix

This fixes yet another software renderer crash, this time relating to sloped FOFs: sometimes the renderer thinks parts of FOFs where the top and bottom heights are the same height are actually the bottom going through the top (in other words a negative height). This causes problems when drawing normal walls around such FOFs since the game obviously doesn't expect negative heights anywhere along the FOF - before slopes, the game could just flip around the top and bottom heights automatically with no problems. This branch also should fix crashes for all genuine cases of negative FOF heights when slopes are involved, I suppose.

Hopefully this stops FuriousFox's SUGOI map crashing for the time being, all seemed fine when I tested it out myself.

See merge request !96

-warp checking for invalid map names

I've noticed a bunch of new people getting the "Cannot warp to map 0 (out of range)" error when testing their custom maps. On asking what map name they used, it was clear they didn't use a MAPxx name at all. Sadly it was not obvious to them that other kind of map names are not accepted by SRB2, so I thought it best we make that more clear in-game.

SRB2 now gives you the error "Cannot warp to map \[your input\] (invalid map name)" if you used -warp with a param that is neither a MAPxx name or a plain number.

See merge request !99

P_FindSpecialLineFromTag crash fix

This fixes the case where an in-level sector or FOF control sector with a tag of -1 or 65535 (seriously, who does that?) can possibly lead to a crash in this function when searching for heat linedef specials in 1st person. And also the same kind of crash any other sort of weird case where the tag number that function uses for searching is -1 or 65535, I suppose!

See merge request !98

Fix R_AddSingleSpriteDef's I_Error messages

Whoops, seems I forgot about this little branch. Basically this fixes how for a character's sprites, a full sprite lump name is displayed instead of just its sprite prefix in the "R_AddSingleSpriteDef: No patches found for [sprite prefix] frame [frame character]" message (unlike when it occurs for non-character sprites), resulting in something like "R_AddSingleSpriteDef: No patches found for PLAYC2C8 frame \^" which does NOT help custom character authors at all as it just confuses them instead. (for the record, the problem would actually with the ^ frame and not the ones displayed after "PLAY")

Oh, and the same problem is also fixed for this similar message: "R_AddSingleSpriteDef: Sprite [sprite prefix] frame [frame character] is missing rotations"

See merge request !95