patch 9.1.0063: GTK code can be improved

Problem:  GTK code can be improved
Solution: Improve GTK code for initial Wayland support
          (lilydjwg)

related: #9639

Signed-off-by: lilydjwg <lilydjwg@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/proto/gui_gtk_x11.pro b/src/proto/gui_gtk_x11.pro
index e85cf20..d019cf0 100644
--- a/src/proto/gui_gtk_x11.pro
+++ b/src/proto/gui_gtk_x11.pro
@@ -13,7 +13,7 @@
 int gui_mch_showing_tabline(void);
 void gui_mch_update_tabline(void);
 void gui_mch_set_curtab(int nr);
-void gui_gtk_set_selection_targets(void);
+void gui_gtk_set_selection_targets(GdkAtom);
 void gui_gtk_set_dnd_targets(void);
 int gui_mch_init(void);
 void gui_mch_forked(void);