patch 8.0.0451: some macros are in lower case

Problem:    Some macros are in lower case.
Solution:   Make a few more macros upper case. Avoid lower case macros use an
            argument twice.
diff --git a/src/ex_cmds.c b/src/ex_cmds.c
index 386183d..898ad41 100644
--- a/src/ex_cmds.c
+++ b/src/ex_cmds.c
@@ -4863,7 +4863,7 @@
 	    }
 	    if (cmd[0] == '\\' && cmd[1] != 0)	/* skip escaped characters */
 		++cmd;
-	    mb_ptr_adv(cmd);
+	    MB_PTR_ADV(cmd);
 	}
 
 	if (!eap->skip)