q3bsp curve collisions (technically it can collide against any triangle mesh)

q3bsp curve collisions (technically it can collide against any triangle mesh)
fixed some severe bugs in the q3bsp traceline code
optimized q3bsp tracebrush code - now uses a bbox for the trace, and reduces it to fit each node it encounters, this caused *IMMENSE* speedups!
optimized q3bsp curve collisions to use bbox culling of triangles (to avoid the cost of generating collision brushes most of the time)

git-svn-id: svn://svn.icculus.org/twilight/trunk/darkplaces@3417 d7cf8633-e32d-0410-b094-e92efae38249