dix: add MASTER_ATTACHED as allowed type for GetMaster().

In some cases, we don't know/care whether we want the master pointer or keyboard
for a device. Add a new type MASTER_ATTACHED to return the master this
device is attached to.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Benjamin Tissoires <tissoire@cena.fr>

include/inputstr.h

@@ -493,6 +493,7 @@ typedef struct _SpriteInfoRec {
 #define MASTER_POINTER          1
 #define MASTER_KEYBOARD         2
 #define SLAVE                   3
+#define MASTER_ATTACHED         4  /* special type for GetMaster */
 
 typedef struct _DeviceIntRec {
     DeviceRec	public;