(Ftranslate_region): Check the buffer multibyteness.

src/editfns.c

@@ -2425,6 +2425,7 @@ It returns the number of characters changed.")
   int cnt;			/* Number of changes made. */
   int size;			/* Size of translate table. */
   int pos;
+  int multibyte = !NILP (current_buffer->enable_multibyte_characters);
 
   validate_region (&start, &end);
   CHECK_STRING (table, 2);
@@ -2445,7 +2446,10 @@ It returns the number of characters changed.")
       int oc;
       int pos_byte_next;
 
-      oc = STRING_CHAR_AND_LENGTH (p, stop - pos_byte, len);
+      if (multibyte)
+	oc = STRING_CHAR_AND_LENGTH (p, stop - pos_byte, len);
+      else
+	oc = *p, len = 1;
       pos_byte_next = pos_byte + len;
       if (oc < size && len == 1)
 	{