patch 8.0.0504: looking up an Ex command is a bit slow

Problem:    Looking up an Ex command is a bit slow.
Solution:   Instead of just using the first letter, also use the second letter
            to skip ahead in the list of commands. Generate the table with a
            Perl script. (Dominique Pelle, closes #1589)

src/version.c

@@ -764,6 +764,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    504,
 /**/
     503,
 /**/