bug#15166: 24.3.50; Isearch for an octal code

[Juri Linkov]

> Recipe from "emacs -Q":
>   C-q 2 0 0 RET M-< C-s C-q 2 0 0 RET
>
> I observe that Isearch fails; it's unable to find the character with
> octal code `200'.

This is due to this special casing in `isearch-quote-char':

      (and enable-multibyte-characters
           (>= char ?\200)
           (<= char ?\377)
           (setq char (unibyte-char-to-multibyte char)))

But in `quoted-insert' the same code is commented out now.
So `isearch-quote-char' should be synced with `quoted-insert'
by adding the same comment from `quoted-insert':

=== modified file 'lisp/isearch.el'
--- lisp/isearch.el     2013-07-05 20:15:32 +0000
+++ lisp/isearch.el     2013-08-23 22:42:25 +0000
@@ -2730,10 +2748,14 @@ (defun isearch-quote-char (&optional cou
        (if (subregexp-context-p isearch-string (length isearch-string))
            (isearch-process-search-string "[ ]" " ")
          (isearch-process-search-char char count))
-      (and enable-multibyte-characters
-          (>= char ?\200)
-          (<= char ?\377)
-          (setq char (unibyte-char-to-multibyte char)))
+      ;; This used to assume character codes 0240 - 0377 stand for
+      ;; characters in some single-byte character set, and converted them
+      ;; to Emacs characters.  But in 23.1 this feature is deprecated
+      ;; in favor of inserting the corresponding Unicode characters.
+      ;; (and enable-multibyte-characters
+      ;;          (>= char ?\200)
+      ;;          (<= char ?\377)
+      ;;          (setq char (unibyte-char-to-multibyte char)))
       (isearch-process-search-char char count))))
 
 (defun isearch-printing-char (&optional char count)