xwayland: don't allow clients to modify the keymap

Xwayland has no way to affect the keymap of the compositor. If clients
modify the keymap, it will stay out of sync with the compositor until
some unspecified time in the future when the compositor sends the keymap
again, which might be never, requiring Xwayland to be restarted.

Signed-off-by: Julian Orth <ju.orth@gmail.com>
Part-of: <https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/1953>

include/inputstr.h

@@ -632,6 +632,7 @@ typedef struct _DeviceIntRec {
     struct _SyncCounter *idle_counter;
 
     Bool ignoreXkbActionsBehaviors; /* TRUE if keys don't trigger behaviors and actions */
+    Bool hasDdxKeymap;              /* TRUE if clients cannot modify the keymap */
 } DeviceIntRec;
 
 typedef struct {