dri_interface: add DRI2_BufferDamage interface

dri_interface: add DRI2_BufferDamage interface

Add a new DRI2_BufferDamage interface to support the
EGL_KHR_partial_update extension, informing the driver of an overriding
scissor region for a particular drawable.

Based on a commit originally authored by:
Harish Krupo <harish.krupo.kps@intel.com>
renamed extension, retargeted at DRI drawable instead of context,
rewritten description

Signed-off-by: Daniel Stone <daniels@collabora.com>
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Acked-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Reviewed-by: Qiang Yu <yuq825@gmail.com>
Tested-by: Qiang Yu <yuq825@gmail.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>