Emit cliprects in the userspace driver as required, rather than

Emit cliprects in the userspace driver as required, rather than
passing them to the kernel.  This works because all drawing commands
in the 965 driver are emitted with the lock held and the batchbuffer
is always flushed prior to releasing the lock.  This allows multiple
cliprects to be dealt with, without replaying entire batchbuffers and
redundantly re-emitting state.