patch 8.1.0137: CI does not run with TCL

Problem:    CI does not run with TCL.
Solution:   Add TCL to the travis config. (Dominique Pelle, closes #3133)
diff --git a/src/version.c b/src/version.c
index 4e88163..9c79148 100644
--- a/src/version.c
+++ b/src/version.c
@@ -790,6 +790,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    137,
+/**/
     136,
 /**/
     135,