Merge remote-tracking branch 'upstream/master'
Merge remote-tracking branch 'upstream/master'
Merge remote-tracking branch 'upstream/master'
Merge remote-tracking branch 'upstream/master'
Merge branch 'master' into next
Merge remote-tracking branch 'upstream/master'
Merge remote-tracking branch 'upstream/master'
Polyobject top/bottom texture + translucency

polyobjects do have top/bottom textures, silly.
And translucency.
Polyobject translucency quick fix.

I realise what I did before may cause FOF's in the same sector to not be
drawn, if they were before.
else added

less redundancy.
Fix certain textures with holes in

see: CEZ1 skybox in linear filtermodes.
OpenGL Fade masks

I think I've done this all right, someone correct me if I haven't.
Merge branch 'master' into next
Merge the dedicatedserver and server global variables

Previously in Lua, dedicatedserver would only return true if the player running the script was the one hosting the dedicated server. In all other cases, it would return nil. This fixes it to point to the server host no matter what.
Use gcc_struct on ATTRPACK too
Merge remote-tracking branch 'origin/master' into next
OpenGL: Fix sky drawing

sky positioning and scaling more correct compared to software.
OpenGL: Sky culling

Gets rid of stuff being drawn where the sky should be being drawn.
Quick sky fix

Avoid Z-Fighting on the depth wall with the regular walls to stop the
possibility of regular walls being made partially invisible.
Quick sky fix 2

walls not extending down when a thok barrier has top textures and both
ceilings have sky.