patch 8.1.2134: modifier keys are not always recognized

Problem:    Modifier keys are not always recognized.
Solution:   Handle key codes generated by xterm with modifyOtherKeys set.
            Add this to libvterm so we can debug it.
diff --git a/src/version.c b/src/version.c
index acbcc2d..7289c9b 100644
--- a/src/version.c
+++ b/src/version.c
@@ -754,6 +754,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2134,
+/**/
     2133,
 /**/
     2132,