patch 8.1.2191: when using modifyOtherKeys CTRL-X mode may not work

Problem:    When using modifyOtherKeys CTRL-X mode may not work.
Solution:   Recognize a control character also in the form with a modifier.
diff --git a/src/version.c b/src/version.c
index caf8ccf..c9c0943 100644
--- a/src/version.c
+++ b/src/version.c
@@ -742,6 +742,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2191,
+/**/
     2190,
 /**/
     2189,