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)
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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/