Add language about implicit flush and command completion

Copied language from the glXSwapBuffers manual page about the implicit
glFlush and expected command completion.  This just codifies what
people already expect from glXCopySubBufferMESA.  The intention of
this command is to work like glXSwapBuffers but on a sub-rectangle of
the drawable.

Acked-by: Brian Paul <brianp@vmware.com>
1 file changed