dri2proto: Changes to 'dri2-swapbuffers'

[Jesse Barnes]

New branch 'dri2-swapbuffers' available with the following commits:
commit 9b5ef83c0b9ef0239ac82adfa9a816f195074dcb
Author: Jesse Barnes <jbarnes at virtuousgeek.org>
Date:   Fri May 1 14:41:55 2009 -0700

    Add SwapBuffers request
    
    Add a SwapBuffers request for requesting a front<->back swap.  Returns a
    whole new set of buffers to the client to allow for triple buffering
    etc.