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)
diff --git a/src/version.c b/src/version.c
index 3e86c40..48cd6d2 100644
--- a/src/version.c
+++ b/src/version.c
@@ -795,6 +795,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    368,
+/**/
     367,
 /**/
     366,