patch 7.4.2017

Problem:    When there are many errors adding them to the quickfix list takes
            a long time.
Solution:   Add BLN_NOOPT.  Don't call buf_valid() in buf_copy_options().
            Remember the last file name used.  When going through the buffer
            list start from the end of the list.  Only call buf_valid() when
            autocommands were executed.

src/option.c

@@ -10634,12 +10634,6 @@ buf_copy_options(buf_T *buf, int flags)
     int		dont_do_help;
     int		did_isk = FALSE;
 
-    /*
-     * Don't do anything if the buffer is invalid.
-     */
-    if (buf == NULL || !buf_valid(buf))
-	return;
-
     /*
      * Skip this when the option defaults have not been set yet.  Happens when
      * main() allocates the first buffer.