(isearch-quote-char): Don't assume character codes

0200 - 0237 stand for characters in some single-byte character
charset.

lisp/isearch.el

@@ -1189,13 +1189,13 @@ and the meta character is unread so that it applies to editing the string."
   "Quote special characters for incremental search."
   (interactive)
   (let ((char (read-quoted-char (isearch-message t))))
-    ;; Assume character codes 0200 - 0377 stand for 
-    ;; European characters in Latin-1, and convert them
-    ;; to Emacs characters.
+    ;; Assume character codes 0240 - 0377 stand for characters in some
+    ;; single-byte character set, and convert them to Emacs
+    ;; characters.
     (and enable-multibyte-characters
-	 (>= char ?\200)
+	 (>= char ?\240)
 	 (<= char ?\377)
-	 (setq char (+ char nonascii-insert-offset)))
+	 (setq char (unibyte-char-to-multibyte char)))
     (isearch-process-search-char char)))
 
 (defun isearch-return-char ()