Add syncsdk.h, a new xorg SDK header.  It
contains SyncVerifyFence() and the helper
functions that use it to look up fence sync
objects.  Exporting this functionality in an
SDK header allows 3rd party extensions to
look up fence objects in their interop APIs.

Signed-off-by: James Jones <jajones@nvidia.com>
Reviewed-by: Aaron Plattner <aplattner@nvidia.com>
Reviewed-by: Robert Morell <rmorell@nvidia.com>
Reviewed-by: Adam Jackson <ajax@redhat.com>