patch 8.2.4815: cannot build with older GTK version

Problem:    Cannot build with older GTK version.
Solution:   Use gtk_window_get_size() instead of gdk_window_get_width() and
            gdk_window_get_height(). (Ernie Rael, closes #10257)
diff --git a/src/version.c b/src/version.c
index c1096e2..3dc22d0 100644
--- a/src/version.c
+++ b/src/version.c
@@ -747,6 +747,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    4815,
+/**/
     4814,
 /**/
     4813,