patch 8.1.2120: some MB_ macros are more complicated than necessary

Problem:    Some MB_ macros are more complicated than necessary. (Dominique
            Pelle)
Solution:   Simplify the macros.  Expand inline.
diff --git a/src/ops.c b/src/ops.c
index e82a66b..aa68584 100644
--- a/src/ops.c
+++ b/src/ops.c
@@ -3223,7 +3223,7 @@
 	    while (ptr[col] != NUL
 		    && !vim_isdigit(ptr[col])
 		    && !(doalp && ASCII_ISALPHA(ptr[col])))
-		col += MB_PTR2LEN(ptr + col);
+		col += mb_ptr2len(ptr + col);
 
 	    while (col > 0
 		    && vim_isdigit(ptr[col - 1])
@@ -3242,7 +3242,7 @@
 		&& !vim_isdigit(ptr[col])
 		&& !(doalp && ASCII_ISALPHA(ptr[col])))
 	{
-	    int mb_len = MB_PTR2LEN(ptr + col);
+	    int mb_len = mb_ptr2len(ptr + col);
 
 	    col += mb_len;
 	    length -= mb_len;