Xext: Enable MIT-SHM FD-passing request definitions only when possible

Check to see if xtrans FD passing is available and use that to
advertise the appropriate version of the SHM extension

Signed-off-by: Keith Packard <keithp@keithp.com>
Reviewed-by: Alan Coopersmith <alan.coopersmith@oracle.com>

include/protocol-versions.h

@@ -93,7 +93,11 @@
 
 /* SHM */
 #define SERVER_SHM_MAJOR_VERSION		1
+#if XTRANS_SEND_FDS
+#define SERVER_SHM_MINOR_VERSION		2
+#else
 #define SERVER_SHM_MINOR_VERSION		1
+#endif
 
 /* Sync */
 #define SERVER_SYNC_MAJOR_VERSION		3