input: use ro_anonymous_file to minimize duplication of keymap files

Since version 7 clients must use MAP_PRIVATE to map the keymap fd so we
can use memfd_create in os_ro_anonymous_file_get_ref using
RO_ANONYMOUS_FILE_MAPMODE_PRIVATE, for older version we use
RO_ANONYMOUS_FILE_MAPMODE_SHARED to be compatibile with MAP_SHARED.

Signed-off-by: Sebastian Wick <sebastian@sebastianwick.net>

include/libweston/libweston.h

@@ -78,6 +78,7 @@ struct weston_pointer;
 struct linux_dmabuf_buffer;
 struct weston_recorder;
 struct weston_pointer_constraint;
+struct ro_anonymous_file;
 
 enum weston_keyboard_modifier {
 	MODIFIER_CTRL = (1 << 0),
@@ -704,8 +705,7 @@ weston_pointer_start_drag(struct weston_pointer *pointer,
 		       struct wl_client *client);
 struct weston_xkb_info {
 	struct xkb_keymap *keymap;
-	size_t keymap_size;
-	char *keymap_string;
+	struct ro_anonymous_file *keymap_rofile;
 	int32_t ref_count;
 	xkb_mod_index_t shift_mod;
 	xkb_mod_index_t caps_mod;