Add RandR leases support

Signed-off-by: Keith Packard <keithp@keithp.com>
(Ported from xserver commit e4e3447603b5fd3a38a92c3f972396d1f81168ad)
Signed-off-by: Michel Dänzer <michel.daenzer@amd.com>
(Ported from amdgpu commit 61040bdfa360975614fb47aa7ea1b3a1abac3427)
Acked-by: Alex Deucher <alexander.deucher@amd.com>