updating ent_geometry rendermesh

update vertex positions in gpu mem instead
of rebuilding the entire mesh
save update state for each geometric object
updating of cylinder edges

only rebuild cylinder edges which geometry changed
GiantBuffer: assert that freelist is sorted
GiantBuffer: sort freelist with insertion sort
ENT_Geometry: properly destroy rendermesh
GiantBuffer: fixed memory allocation bug

free bufsegs are split to fit requested allocation size
to avoid small allocations occupying large bufsegs