wayland: Support the cursor-shape protocol

If present, use the cursor-shape protocol instead of manually
updating a pointer surface. This commit supports both v1 of the
protocol and the (still unmerged) v2 additions to the enumeration.

This was tested with both kwin and mutter.

(cherry picked from commit a63d6d1dc7a8ebdf61c682196f89917846cbe8ac)

gdk/wayland/gdkprivate-wayland.h

@@ -89,6 +89,8 @@ gboolean   _gdk_wayland_display_supports_cursor_color (GdkDisplay *display);
 void       gdk_wayland_display_system_bell (GdkDisplay *display,
                                             GdkWindow  *window);
 
+const char *_gdk_wayland_cursor_get_name (GdkCursor *cursor);
+
 struct wl_buffer *_gdk_wayland_cursor_get_buffer (GdkCursor *cursor,
                                                   guint      image_index,
                                                   int       *hotspot_x,