reduced memory usage by around 20MB (no longer allocates interleaved

reduced memory usage by around 20MB (no longer allocates interleaved
vertex arrays unless running D3D renderpath, now uses R_FrameData_Alloc
a lot more to avoid large static arrays)
R_FrameData system now never fails an alloc request (resizing as
needed), and has a mark system allowing space to be relinquished after
brief uses such as batch buffers
removed r_vertexposition_t as it was redundant (just use vertex3f)
gl_mesh_separatearrays cvar removed (vid.useinterleavedarrays is now used instead)
audited RSurf_PrepareVertices calls to make sure BATCHNEED_NOGAPS is
properly used

git-svn-id: svn://svn.icculus.org/twilight/trunk/darkplaces@10711 d7cf8633-e32d-0410-b094-e92efae38249