patch 8.1.2120: some MB_ macros are more complicated than necessary

Problem:    Some MB_ macros are more complicated than necessary. (Dominique
            Pelle)
Solution:   Simplify the macros.  Expand inline.

src/version.c

@@ -753,6 +753,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    2120,
 /**/
     2119,
 /**/