patch 8.2.3491: xpm2 filetype dection is not so good

Problem:    xpm2 filetype dection is not so good.
Solution:   Adjust the check for xpm2. (closes #8914)
diff --git a/src/version.c b/src/version.c
index 074c896..5fe4dcc 100644
--- a/src/version.c
+++ b/src/version.c
@@ -758,6 +758,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    3491,
+/**/
     3490,
 /**/
     3489,