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/charset.c b/src/charset.c
index 18a6935..2091d23 100644
--- a/src/charset.c
+++ b/src/charset.c
@@ -1530,7 +1530,7 @@
 {
     char_u	*p = q;
 
-    while (vim_iswhite(*p)) /* skip to next non-white */
+    while (VIM_ISWHITE(*p)) /* skip to next non-white */
 	++p;
     return p;
 }