patch 8.1.1474: 'ttybuiltin' is not tested

Problem:    'ttybuiltin' is not tested.
Solution:   At least test that it doesn't break things.
diff --git a/src/version.c b/src/version.c
index cd138ab..a422cb0 100644
--- a/src/version.c
+++ b/src/version.c
@@ -768,6 +768,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1474,
+/**/
     1473,
 /**/
     1472,