patch 8.1.1137: xterm mouse wheel escape sequence is not tested

Problem:    Xterm mouse wheel escape sequence is not tested.
Solution:   Add a test using low-level input. (Dominique Pelle, closes #4221)
diff --git a/src/version.c b/src/version.c
index 6b428b4..d2da9fc 100644
--- a/src/version.c
+++ b/src/version.c
@@ -772,6 +772,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1137,
+/**/
     1136,
 /**/
     1135,