Gas jets, fan objects, springs and slopes

Whoop whoop whoop minor bugs that only get noticed due to weird experiments whoop whoop whoop

* For gas jets only: the object's standingslope is ALWAYS null. No drifting down the slope for you.
* For gas jets and fan objects: Now checks whether the player's top is below the bottom of the launcher, instead of its bottom. zdist calculation not affected, since it's signed and okay with being negative by about the height of the player.
* For all 3: the player's standingslope is NULL'd so the player isn't launched off at a wacky angle if they're standing on a slope then walk into the thing.

See merge request !91

Re-factoring AA tree code from m_misc.c/m_misc.h into its own files

What the title says. The AA tree-related code now lives in the files m_aatree.c and m_aatree.h. Part of why I did this was to solve this m_misc.h/w_wad.h cyclic dependency problem (involving MAX_WADPATH and AA trees themselves) mentioned in the now-removed comments, another reason was ...only OpenGL uses AA trees at all, why include the relevent structs/functions/otherwise anywhere except where is necessary (which is very few files as it turns out)?

Otherwise, it just looked better on its own rather than mixed with all the other stuff already in the m_misc files. Not really important or anything affecting gameplay at all I guess.

See merge request !82

For GCC 6.1 builds

I do not know what I was doing:

NULL checks

building without BLUA support

functions that do not depend on outside vars should be tagged with "const", AKA, FUNCMATH

See merge request !89

- Now checks whether the player's top is below the bottom of the fan/gas jet, instead of its bottom. zdist calculation not affected.
- mo->standingslope is NULL'd so the player isn't launched off at a wacky angle. (I also did this for springs, since Prime mentioned it was a problem for them too.)

Some slope improvements/fixes (plus P_GetMobjGravity)

Dear Red, I did some things.

* Made the slope flag SL_NOPHYSICS actually have an effect like we wanted to, but didn't get around to implementing yet - activated by setting the slope's linedef flags to have ML_NOSONIC.
* Made downhill slope thrusts proportional to an object's gravity and friction.
* To make the above happen - seperated out the gravity value finding code in P_CheckGravity into a seperate function, P_GetMobjGravity. (p_mobj.c, p_local.h) I also made this function available to Lua.
* Turned those PANIC n console messages (which would inevitably be followed up with a crash, since we're accessing invalid memory immediately after) into a descriptive I_Error.
* Put the SRB2CB type-shimming behind an ESLOPE_TYPESHIM ifdef.
* Removed SPRINGCLEAN-ifdef'd code.
* Cleaned up some eosteric comments.
* NEW SINCE RED +1'd THIS: The teetering code now takes slopes into account pretty well. There are edge circumstances as outlined in commit 9d221f4f, but this is unilaterally better behaviour in every way and the teetering code was kind of a mess anyways.
* NEW SINCE RED AND ALAM +1'd THIS: P_ReverseQuantiseMomentumToSlope. Simple function that replaces the inverse angle stuff (which also wasn't using InvAngle, just ANGLE_MAX - angle - which is inaccurate!!)

Current testing files available at /toaster/slptst3.wad and /toaster/gravitytest.lua on the ftp.

I want to do more to the branch like implement SL_ANCHORVERTEX in the near future, but this is probably safe to merge in its current state.

See merge request !77

Climbing on one-sided linedefs

Does what it says on the tin. You couldn't before, now you can.

With this branch, thok barriers are now completely optional for maps with no aesthetic need for sky-topped walls. All the bugs and complications that exist with climbing right now still exist, except now there's one less issue making them suck forever and now Nev3r will be very happy.

Do I need a testing .wad? It's... not that hard to create a very small map and go nuts with Knuckles in it. I have one, but uploading it to the ftp almost feels insulting.

See merge request !90

The whole thing needs a refactor in general, but it's almost 2am here, I need my sleeb, and this fix would probably break something with 2.1 climbing if I made it any more/less (depending on viewpoint) complicated.

...completely misunderstood the reasons we weren't merging toast_slopes, mom holy fuck i'm stupid and bad

Enjoy your slopes without physics, people :D

# Conflicts:
#	src/p_user.c

Revert "Changed teetering to match the discoveries made about it in the sectorlist_traversal branch in a way that matches my revamps here, since I DID change a lot."

This reverts commit 19b186e5.

This reverts commit 1723bb55.

Sectorlist traversal

MOM GET THE CAMERA

There's a LOT of code in the source that ended up mixing m_snext (the node for the next thing in the sector's thinglist) and m_tnext (the node for the next sector in the thing's sectorlist), so I renamed the following:

* m_snext ==> m_thinglist_next
* m_sprev ==> m_thinglist_prev
* m_tnext ==> m_sectorlist_next
* m_tprev ==> m_sectorlist_prev

Then, I changed all the instances where the code was trying to go m_thinglist_next on a mobj's touching_sectorlist (which would've just gone to the node for the next thing in the same sector, instead of the node for the next sector for the same thing). Notable samples:

* FF_SHATTER blocks now disappear the moment you go into their sector. You still can't give FF_SOLID to them because in that case they will still stop you if you never enter their sector at all (ie - clip on corners), but having them nonsolid no longer allows you to phase through entirely without busting them (which was the whole downside of making them intangible in the first place).
* You can now bump into multiple Mario blocks at a time, even if you're not exclusively in their sector.
* No more getting randomly stopped on the edges of bouncy FOFs.
* Landing on polyobjects might behave a little more consistently at the edge of their host sector.
* Teetering did a SHITTON of code that basically never got executed, and then had directly-blockmap-accessing code as a backup. The code was activatable by replacing the m_thinglist_next with m_sectorlist_next, but it behaved SUPER differently from what we're used to with teetering (if the player mobj's edge was JUST off the edge of a platform, you ended up in teetering frames - even if it looked like you could stand) so I ended up removing that section entirely.

Any objections?

See merge request !85

Some other software fixes/changes

Some other software fixes/changes I've made

* Change 1: single-sided linedef midtextures (read: not double-sided linedefs, but single-sided) now don't skew if Effect 2 is checked. Before, there wasn't any ability for software to disable skewing for them. =V
* Change 2: PolyObject back side midtextures now return to being where they should be. Had to make a hack to fix this though.

See merge request !86

Fixes and changes related to the act of setting up a level (in other words, setup fixes)

Changes made in this branch so far:
* a REJECT lump of zero length (NOT to be confused with a REJECT lump of non-zero length with all-zeros, just to clarify) should no longer cause problems with netgames and otherwise. The game now checks if the lump exists, has the right name, and length is not zero - if it fails any of these, the REJECT lump is not loaded and P_CheckSight won't be allowed to use it. This means ZDBSP (no reject) should be safe(r) to use now!
* there's now a simple devmode-only message (requires "Setup" mode) if a sector is found to have no lines at all during setup. It's a far cry from the plot to I_Error the game I once had for that unsusal scenario, but such a level still works anyway so whatever.

See merge request !87

FF_REVERSEPLATFORM clipping

Ran into an issue whilst testing out one last feature (there's always one more...) for flat_alignment_revamp. This is a backported fix.

The bug was such that if you're falling through a platform with FF_REVERSEPLATFORM and not FF_PLATFORM, you'll be pushed downwards such that your head is against the bottom of the FOF. This just checks momz is greater than zero if it has FF_REVERSEPLATFORM to make sure it's okay to set ceilingz. (OR the alternative in reverse gravity.)

No test map because this was originally done for internal. Instead, test it on the other branch's test map.

See merge request !83