st/xorg: handle updates to DamageUnregister API

xserver 1.14.99.2 simplified the DamageUnregister API, by
dropping the drawable argument.
Follow xf86-video-intel and xf86-video-vmware approach and
handle the new API by checking XORG_VERSION_CURRENT.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=71110
Reported-by: Michał Górny <mgorny@gentoo.org>
Reported-by: Vinson Lee <vlee@freedesktop.org>
Tested-by: Vinson Lee <vlee@freedesktop.org>
Reviewed-by: Brian Paul <brianp@vmware.com>
Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>

src/gallium/state_trackers/xorg/xorg_driver.c

@@ -1027,7 +1027,11 @@ drv_close_screen(CLOSE_SCREEN_ARGS_DECL)
 
 #ifdef DRM_MODE_FEATURE_DIRTYFB
     if (ms->damage) {
+#if XORG_VERSION_CURRENT >= XORG_VERSION_NUMERIC(1,14,99,2,0)
+	DamageUnregister(ms->damage);
+#else
 	DamageUnregister(&pScreen->GetScreenPixmap(pScreen)->drawable, ms->damage);
+#endif
 	DamageDestroy(ms->damage);
 	ms->damage = NULL;
     }