zym models are now loaded into the same structs as alias models in memory, this reduc...

zym models are now loaded into the same structs as alias models in memory, this reduces code a lot and gives the full feature set (rtlights/skins)
zym models are now optimized when loading to eliminate duplicate vertex data (one of their more significant design flaws)
mdl/md2/md3 models no longer have stored svector/tvector/normal arrays, instead generating them on demand like skeletal models (this is slower but saves a *lot* of memory)
zym collisions are not implemented (yet)
zym bones are not reported as tags (yet)

git-svn-id: svn://svn.icculus.org/twilight/trunk/darkplaces@4429 d7cf8633-e32d-0410-b094-e92efae38249