Changes with nginx 0.7.17 15 Sep 2008

    *) Feature: now the "directio" directive works on Linux.

    *) Feature: the $pid variable.

    *) Bugfix: the "directio" optimization that had appeared in 0.7.15 did
       not work with open_file_cache.

    *) Bugfix: the "access_log" with variables did not work on Linux; the
       bug had appeared in 0.7.7.

    *) Bugfix: the ngx_http_charset_module did not understand quoted
       charset name received from backend.