patch 8.0.0452: some macros are in lower case

Problem:    Some macros are in lower case.
Solution:   Make a few more macros upper case.
diff --git a/src/ex_cmds2.c b/src/ex_cmds2.c
index 2da38b7..1b5d45d 100644
--- a/src/ex_cmds2.c
+++ b/src/ex_cmds2.c
@@ -5183,7 +5183,7 @@
      * Allow abbreviation, but require at least 3 characters to avoid
      * confusion with a two letter language name "me" or "ct". */
     p = skiptowhite(eap->arg);
-    if ((*p == NUL || vim_iswhite(*p)) && p - eap->arg >= 3)
+    if ((*p == NUL || VIM_ISWHITE(*p)) && p - eap->arg >= 3)
     {
 	if (STRNICMP(eap->arg, "messages", p - eap->arg) == 0)
 	{