Don't call MAYBE_UNIFY_CHAR while processing buffers and strings.

 src/character.c (char_string, string_char): Remove calls to
 MAYBE_UNIFY_CHAR.  See the discussion starting at
 http://lists.gnu.org/archive/html/emacs-devel/2012-09/msg00433.html
 for the details.

src/ChangeLog

+2012-09-25  Eli Zaretskii  <eliz@gnu.org>
+
+	* character.c (char_string, string_char): Remove calls to
+	MAYBE_UNIFY_CHAR.  See the discussion starting at
+	http://lists.gnu.org/archive/html/emacs-devel/2012-09/msg00433.html
+	for the details.
+
 2012-09-25  Chong Yidong  <cyd@gnu.org>
 
 	* xdisp.c (mode_line_inverse_video): Delete obsolete variable.

src/character.c

@@ -126,8 +126,6 @@ char_string (unsigned int c, unsigned char *p)
       c &= ~CHAR_MODIFIER_MASK;
     }
 
-  MAYBE_UNIFY_CHAR (c);
-
   if (c <= MAX_3_BYTE_CHAR)
     {
       bytes = CHAR_STRING (c, p);
@@ -195,8 +193,6 @@ string_char (const unsigned char *p, const unsigned char **advanced, int *len)
       p += 5;
     }
 
-  MAYBE_UNIFY_CHAR (c);
-
   if (len)
     *len = p - saved_p;
   if (advanced)