patch 8.1.1064: no test for output conversion in the GTK GUI

Problem:    No test for output conversion in the GTK GUI.
Solution:   Add a simplistic test.
diff --git a/src/version.c b/src/version.c
index 1fa7429..b8b3c14 100644
--- a/src/version.c
+++ b/src/version.c
@@ -776,6 +776,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1064,
+/**/
     1063,
 /**/
     1062,