ephyr: ignore Xorg multiseat command line options

Multi-seat-capable display managers commonly pass command-line options
like "-novtswitch", "-sharevts", or "-layout seatXXXX" to Xorg server,
but Xephyr currently refuses to start if these options are passed to it,
which may break Xephyr-based single-GPU multiseat setups.

[ajax: shortened summary]

Reviewed-by: Adam Jackson <ajax@redhat.com>
Signed-off-by: Laércio de Sousa <laerciosousa@sme-mogidascruzes.sp.gov.br>

hw/kdrive/ephyr/ephyrinit.c

@@ -356,6 +356,13 @@ ddxProcessArgument(int argc, char **argv, int i)
         EphyrWantNoHostGrab = 1;
         return 1;
     }
+    else if (!strcmp(argv[i], "-sharevts") ||
+             !strcmp(argv[i], "-novtswitch")) {
+        return 1;
+    }
+    else if (!strcmp(argv[i], "-layout")) {
+        return 2;
+    }
 
     return KdProcessArgument(argc, argv, i);
 }