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)

src/version.c

@@ -746,6 +746,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    4815,
 /**/
     4814,
 /**/