merge changes between nginx 1.4.4 and 1.4.5

 Details are as following:

 *) Bugfix: the $ssl_session_id variable contained full session
    serialized instead of just a session id.
    Thanks to Ivan Ristić.

    Changeset: http://hg.nginx.org/nginx/rev/70f4d99ded41

 *) Bugfix: client connections might be immediately closed if deferred
    accept was used; the bug had appeared in 1.3.15.

    Changeset: http://hg.nginx.org/nginx/rev/462ae7eedc68

 *) Bugfix: alerts "zero size buf in output" might appear in logs while
    proxying; the bug had appeared in 1.3.9.

    Changeset:  http://hg.nginx.org/nginx/rev/3b7463b08747

 *) Bugfix: a segmentation fault might occur in a worker process if the
    ngx_http_spdy_module was used.

    Changeset: http://hg.nginx.org/nginx/rev/b8e6297358b5

 *) Bugfix: proxied WebSocket connections might hang right after
    handshake if the select, poll, or /dev/poll methods were used.

    Changeset: http://hg.nginx.org/nginx/rev/560de9681661

    More details are available here:
    http://mailman.nginx.org/pipermail/nginx/2014-January/041839.html

 *) Bugfix: a timeout might occur while reading client request body in an
    SSL connection using chunked transfer encoding.

    Changeset: http://hg.nginx.org/nginx/rev/35b00bcf72fe

    More details are available here:
    http://mailman.nginx.org/pipermail/nginx/2013-November/041178.html

 *) Bugfix: memory leak in nginx/Windows.

    Changeset: http://hg.nginx.org/nginx/rev/fd77e2018652

    Note that this patch is not merged because tengine does not support win32.
Merge pull request #405 from chobits/nginx-update-1.4.5

merge changes between nginx 1.4.4 and 1.4.5