Smooth polyobject movement and other cleanup

See merge request !947

Store waypoints at map load instead of iterating through the thinker list to find them

See merge request !938

I forgot to test OpenGL 

See merge request !953

Encapsulate plane height checks

See merge request !860

# Conflicts:
#	src/hardware/hw_main.c
#	src/p_spec.c

Fix missing sprite column (resolves #135)

See merge request !944

FOF cleanup

See merge request !910

Add missing packet name

See merge request !948

S_StopSoundByID Lua support

See merge request !925

More Demo code cleanup

See merge request !942

Fix A_SignSpin not being usable in Lua or SOC due to an error

See merge request !946

T_PolyObjWaypoint: We can find waypoints in constant time now, so no need to store the waypoint mobj in the thinker anymore

Fix colormap mipmap memory leak on the character select in OpenGL

See merge request !943

Character select in Nights mode.

See merge request !862

Add carry types to Dust devils

See merge request !886

split significant chunks of G_CheckDemoStatus into their own smaller functions, also give writing demo checksums its own little function

Act number tweaks

See merge request !905

Fix window icon being reset when switching renderers on non-Windows platforms

See merge request !898

Fix OpenGL only recording the first frame of unoptimized GIFs

See merge request !928