Remove secplanes

This is just removing SSNTails's old port of ZDoom's secplane code and math, from back when he attempted slopes himself. The slopes we've had since 2.1.15 however do not need these, so we can pretty much toss the code for them out now (nothing uses them anyway).

See merge request !149

Netcode shit

Remove all traces of SSN's old port of ZDoom's secplanes for slopes, since our slopes do not need them

-Fixed broken net commands, thus fixing (or at least greatly improving) chat/commands/joins/leaves and possibly other annoying bugs
-Updated packet name list so the debug file no longer shows garbage packet names
-Replaced byte values with actual net command names in the debug file. Only the first net command in a packet will be shown though
-Added a MOBJCONSISTANCY define that makes the game takes all revelant mobjs to be counted in the synch seed
-Added a PACKETDROP define that adds two console commands "drop" and "droprate" to simulate bad internet by dropping packets
-Added/changed comments here in there in the netcode
-Fixed a minor error that would ignore one of the urgent ack slots
-Added a space between the map name and "zone" for the messages shown in a joiner's console

(Fixes LSHIFT typing D repeatedly into chat)

Hook optimisation

Zlib pkgconfig

Linux build to include libgme by default

See merge request !116

Generic mobj hooks are now run before mobjtype-specific mobj hooks, and player/linedef executor hooks now have their own lists

readme.txt duplicated, also incorrect

readme.txt should be README.md

SDL2 i_video.c code cleanup

Made some code look a bit neater, removed the need for some SDL2STUBs Fury placed, vid_info console command actually kind of has a use again, etc

See merge request !138

Revert "(Messiness warning) attempt to start using SDL_SetRelativeMouseMode instead of the old hacks of making the mouse do movement without leaving the window and be hidden"

This reverts commit 347b5318.

(Too experimental, may end up adding new bugs; let's just keep it to clean up for now)

(Messiness warning) attempt to start using SDL_SetRelativeMouseMode instead of the old hacks of making the mouse do movement without leaving the window and be hidden

Seems to work so far though

This way it's easier by eye to see from the list which SDL scancode maps to which SRB2 key code

(Apparently SDLK_LMETA/SDLK_RMETA don't exist anymore in SDL2 anyway?)

This means the console command vid_info also works properly too now (well, it does nothing in OpenGL mind)

Turns out sdl12's version of this function only did stuff for DC/GP2X ports; support for them have been cut out for SDL2, so for now let's just not use the function at all

HWR_DrawFill support for V_NOSCALESTART

This fixes the console selection highlighting being wrongly positioned and sized for OpenGL.

See merge request !135

Started work on making HWR_DrawFill support V_NOSCALESTART properly ...so far I've got the console text select highlight in the right place outside of 320x200 (and 320x200 is still fine), but for whatever reason it's too large in width and height

Oh well, we're part of the way there, anyway

Console improvements

* Unused console backgrounds no longer take up memory
* Input cursor can now move left and right
* Support for selections (Shift-arrow keys, CTRL-A, etc)
* Clipboard support (CTRL-C to copy, CTRL-V to paste, CTRL-X to cut)
* Fixed handling of simultaneous modifier key presses

https://dl.dropboxusercontent.com/u/3518218/21/console.gif

None of this affects chat yet, that's not part of the console. I'll look at it later.

See merge request !133

MD2 limits check hotfix

Fixing slight mistake made in merge request !132 that someone else spotted, no real explanation needed

See merge request !134

MD2 vertex/frame/triangle/etc limits checking

Fix for this bug: http://mb.srb2.org/showthread.php?t=42099

The model reading code didn't properly check if the model had too many vertices, so models with higher counts freely broke the game. This fix now stops that and prints an error message if that is the case.

However, it seems some models happily exceed other limits such as texcoords without problem (to my knowledge), so I've not bothered with checking those limits for now. Perhaps this could be a time to discuss if we need to change such limits again or not? Either way, one can easily uncomment my lines for checking texcoords/skins/triangles limits later if needed.

EDIT: I've allowed checking for triangle and frame limits too now, after some discussion.

See merge request !132

MobjThinker, MobjCollide and MobjMoveCollide hooks are now directly linked to the mobjtype they belong to, so you no longer iterate through all existing hooks.