CSQC fixes (less broken, still not spec compliant)

CSQC fixes (less broken, still not spec compliant)
CSQC can now link the same entity multiple times (each time modified differently) as per the CSQC spec (this is mainly useful for rendering multi-model players based on one csqc entity, like Quake3's cgame does)
changed DrawQ functions to automatically set up 2D rendering if previous rendering was of a 3D view (necessary change for proper CSQC support)
changed QuakeC rint builtin implementation to handle very large values (outside of int range) and possibly run a little bit faster, note that it still rounds toward the nearest integer, away from zero (as intended)
refactored gun bob, damage kick fade, and stair smoothing code to eliminate a 'multiple fade steps per frame' bug
renamed the misnamed VM_ftoi function to VM_ftoe, in accordance with the menu QC builtin ftoe

git-svn-id: svn://svn.icculus.org/twilight/trunk/darkplaces@6568 d7cf8633-e32d-0410-b094-e92efae38249