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/memline.c b/src/memline.c
index f9852e5..723bcd4 100644
--- a/src/memline.c
+++ b/src/memline.c
@@ -2028,7 +2028,7 @@
 	if (s != NULL)
 	{
 	    STRCPY(s, f);
-	    for (d = s; *d != NUL; mb_ptr_adv(d))
+	    for (d = s; *d != NUL; MB_PTR_ADV(d))
 		if (vim_ispathsep(*d))
 		    *d = '%';
 	    d = concat_fnames(dir, s, TRUE);
@@ -4015,7 +4015,7 @@
 
 #ifdef WIN3264
     if (retval != NULL)
-	for (t = gettail(retval); *t != NUL; mb_ptr_adv(t))
+	for (t = gettail(retval); *t != NUL; MB_PTR_ADV(t))
 	    if (*t == ':')
 		*t = '%';
 #endif
@@ -4154,7 +4154,7 @@
 	if (buf_fname == NULL)
 	    buf_fname = buf->b_fname;
 	else
-	    for (t = gettail(buf_fname); *t != NUL; mb_ptr_adv(t))
+	    for (t = gettail(buf_fname); *t != NUL; MB_PTR_ADV(t))
 		if (*t == ':')
 		    *t = '%';
     }