patch 7.4.2123

Problem:    No new style test for diff mode.
Solution:   Add a test.  Check that folds are in sync.

src/version.c

@@ -763,6 +763,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    2123,
 /**/
     2122,
 /**/