Bug #45286: compilation warnings on mysql-5.0-bugteam on MacOSX

Implemented a way to circumvent the always true comparison by
having nested macros (as suggested on review).

cmd-line-utils/readline/chardefs.h

@@ -59,7 +59,8 @@
 #define largest_char 255		    /* Largest character value. */
 
 #define CTRL_CHAR(c) ((c) < control_character_threshold && (((c) & 0x80) == 0))
-#define META_CHAR(c) ((c) > meta_character_threshold && (c) <= largest_char)
+#define META_BYTE(c) ((c) > meta_character_threshold)
+#define META_CHAR(c) (META_BYTE(c) && (c) <= largest_char)
 
 #define CTRL(c) ((c) & control_character_mask)
 #define META(c) ((c) | meta_character_bit)

cmd-line-utils/readline/display.c

@@ -1888,7 +1888,7 @@ rl_character_len (c, pos)
 
   uc = (unsigned char)c;
 
-  if (META_CHAR (c))
+  if (META_BYTE (uc))
     return ((_rl_output_meta_chars == 0) ? 4 : 1);
 
   if (uc == '\t')