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/

Added 1 new commit:

• 1530183d - Fix multiple solid midtexture-related issues:

bjerk

EDIT: okay i actually went back and tested this thoroughly instead of just CODE reviewing exclusively, this works out just fine

<Sapheros> (seriously when's [Sky Labyrinth] gettign fixed for netgames?) <TehRealSalt> whenever mi's fix gets accepted <toaster> did you know? <toaster> the biggest problem is testing <toaster> so merge it into your twoonefifteenandahalf exe and give it a shot both with sky labyrinth and normal levels <toaster> And then I'll be able to vounch for it and get it merged <Kogasa> mergeboys <toaster> W E W G I T ............................................... <TehRealSalt> just tried it; works with no issue on my end c: <TehRealSalt> gonna test MI's cutscene fix too <toaster> TehRealSalt: did you test it in normal levels <TehRealSalt> yes, i did <toaster> cool

Added 1 new commit:

• 2a6a21a4 - Solid midtextures now account for "infinite" repeats

Status changed to merged

mentioned in commit 454b705d