Merge PM_FlyMove and PM_NoclipMove into PM_GhostMove.
Nuke spectator door teleporters and allow spectators to noclip through movers.

Note that this uses an existing hack in the server side trace code. The client
will trace differently, leading to lag-dependent jerks when flying through
movers. The next step will be extending the base trace code's filtering to
allow the exclusion of content types.
Add a skip mask to all traces, which allows to selectively ignore content types.

This commit breaks VM/Engine backwards compatibility.
More tracing related cleanup.
Tentatively extend trace (skip-)masks to entities on both client and server side.

Spectators noclip through doors again (broken in 80285be).
Increase default spectator fly speed and decrease its bounding box.
Merge remote-tracking branch 'origin/master' into specmove

Conflicts:
	src/gamelogic/cgame/cg_draw.c
Merge pull request #334 from Unvanquished/specmove

Allow spectators to noclip through doors, instead of teleport.