patch 8.1.1155: termcodes tests can be improved

Problem:    Termcodes tests can be improved.
Solution:   Add helper functions to simplify tests.  Dragging statusline for
            xterm and sgr. (Dominique Pelle, closes #4237)
diff --git a/src/version.c b/src/version.c
index 022fc43..de7a99d 100644
--- a/src/version.c
+++ b/src/version.c
@@ -772,6 +772,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1155,
+/**/
     1154,
 /**/
     1153,