Buffers: used VRAM returns a correct value when the buffer is null
Bugfix: buffer pool: fixed size indices
Buffer pool: bug in RFlushBufferPool()
Bugfix: vertex buffer: RGetVertexBufferSize() now returns the correct value
Added buffer fetches: SCE_RInstantBufferFetch() and
      SCE_RInstant{Vertex,Index}BufferFetch()
Fixed SCE_RClearBufferPool() on nvidia
Removed deprecated GL_MAX_TEXTURE_UNITS query