patch 8.1.0368: GTK code has too many #ifdefs and GTK 2.10 building fails

Problem:    GTK code has too many #ifdefs and building fails with GTK 2.10.
Solution:   Always use gtk_widget_get_window() and define it for older GTK
            versions. (Ken Takata, closes #3421)

src/version.c

@@ -794,6 +794,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    368,
 /**/
     367,
 /**/