updated for version 7.4.439

Problem:    Duplicate message in message history.  Some quickfix messages
            appear twice. (Gary Johnson)
Solution:   Do not reset keep_msg too early. (Hirohito Higashi)

src/main.c

@@ -1249,9 +1249,9 @@ main_loop(cmdwin, noexmode)
 		char_u *p;
 
 		/* msg_attr_keep() will set keep_msg to NULL, must free the
-		 * string here. */
+		 * string here. Don't reset keep_msg, msg_attr_keep() uses it
+		 * to check for duplicates. */
 		p = keep_msg;
-		keep_msg = NULL;
 		msg_attr(p, keep_msg_attr);
 		vim_free(p);
 	    }