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/window.c b/src/window.c
index c9771af..43c9ed2 100644
--- a/src/window.c
+++ b/src/window.c
@@ -6127,7 +6127,7 @@
      */
     ptr = line + col;
     while (*ptr != NUL && !vim_isfilec(*ptr))
-	mb_ptr_adv(ptr);
+	MB_PTR_ADV(ptr);
     if (*ptr == NUL)		/* nothing found */
     {
 	if (options & FNAME_MESS)