DRI3/Present fixes for Mesa 10.3+

[Mario Kleiner]

Hi

Here three patches against mesa to fix use of the OML_sync_control
extension under DRI3/Present and restore behaviour compatible to
the DRI2 implementation, so applications like mine, which were written
and tested against DRI2, don't fail miserably under the new backend.

Tested on Intel HD Ironlake, Intel HD-4000 Ivybridge and nouveau with
NVidia GeForce 330M, on single and dual-display, also with special
timing test equipment to confirm proper behaviour wrt. swap scheduling
and swap completion timestamping.

Together with XOrg-1.16.2 + a set of patches with fixes for the X-Server
i sent out earlier, these patches make users of OML_sync_control and
INTEL_swap_events mostly work correctly under DRI3/Present, at least
with the sna and uxa backends on Intel-ddx and the new dri3/present exa
backend on nouveau-ddx.

Could these patches please also get included into a Mesa 10.3.x stable
update?

Thanks,
-mario