experimental: do not auto allocate a skeletonobject when a CSQC model just uses frame...

experimental: do not auto allocate a skeletonobject when a CSQC model just uses frame based animation (NOTE: this MAY even cause crashes, please test, I just can't find any case where that object is really required); this moves blending of frame based animations back into Mod_Skeletal_AnimateVertices again (if this commit causes worse performance, a different course of action may be reverting it, and making sure a skeletonobject is ALWAYS created, even for SVQC managed legacy entities)

git-svn-id: svn://svn.icculus.org/twilight/trunk/darkplaces@10550 d7cf8633-e32d-0410-b094-e92efae38249
::stable-branch::merge=56712b26644459a90ad48b8a796abdf1b0176dee