patch 8.1.1181: tests for mouse clicks are a bit flaky

Problem:    Tests for mouse clicks are a bit flaky when run in an interactive
            terminal.
Solution:   Use "xterm2" instead of "xterm" for 'ttymouse' to avoid spurious
            drag events.
diff --git a/src/version.c b/src/version.c
index d6a3940..cef19e8 100644
--- a/src/version.c
+++ b/src/version.c
@@ -772,6 +772,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1181,
+/**/
     1180,
 /**/
     1179,