patch 8.1.1311: aborting an autocmd with an exception is not tested

Problem:    Aborting an autocmd with an exception is not tested.
Solution:   Add a test.  Also shows how to abort a command by throwing an
            exception.
diff --git a/src/version.c b/src/version.c
index 57aff32..a9b376e 100644
--- a/src/version.c
+++ b/src/version.c
@@ -768,6 +768,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1311,
+/**/
     1310,
 /**/
     1309,