patch 7.4.1402
Problem:    GTK 3 is not supported.
Solution:   Add GTK 3 support. (Kazunobu Kuriyama)
diff --git a/src/gui_beval.h b/src/gui_beval.h
index 859c081..ead0fb1 100644
--- a/src/gui_beval.h
+++ b/src/gui_beval.h
@@ -11,7 +11,11 @@
 #define GUI_BEVAL_H
 
 #ifdef FEAT_GUI_GTK
-# include <gtk/gtkwidget.h>
+# ifdef USE_GTK3
+#  include <gtk/gtk.h>
+# else
+#  include <gtk/gtkwidget.h>
+# endif
 #else
 # if defined(FEAT_GUI_X11)
 #  include <X11/Intrinsic.h>