patch 8.1.0412: cannot build with GTK 2.4

Problem:    Cannot build with GTK 2.4.
Solution:   Add back a few #ifdefs. (Ken Takata, closes #3447)
            Also support older GTK. (Tom Christensen)
diff --git a/src/version.c b/src/version.c
index e6cb7ba..4631f24 100644
--- a/src/version.c
+++ b/src/version.c
@@ -795,6 +795,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    412,
+/**/
     411,
 /**/
     410,