patch 9.1.0915: GVim: default font size a bit too small

Problem:  GVim: default font size a bit too small
Solution: increase guifont size to 12 pt on GTK builds
          of gVim (matveyt).

fixes: #16172
closes: #16178

Signed-off-by: matveyt <matthewtarasov@yandex.ru>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/version.c b/src/version.c
index 1ae3f53..07bb851 100644
--- a/src/version.c
+++ b/src/version.c
@@ -705,6 +705,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    915,
+/**/
     914,
 /**/
     913,