-Add fence sync objects

-Add fence sync devPrivates

-Add a X sync module screen private

-Add wrappable functions to create and destroy
 fence sync objects

-Give fence sync objects wrappable functions to
 trigger, test, and reset their 'triggered' value.

-Give fence sync objects wrappable functions to
 notify driver when adding/removing triggers to/
 from the sync object.

Signed-off-by: James Jones <jajones@nvidia.com>
Reviewed-by: Keith Packard <keithp@keithp.com>