merge changes between nginx 1.4.6 and 1.4.7

 Details are as following:

 *) Security: a heap memory buffer overflow might occur in a worker
    process while handling a specially crafted request by
    ngx_http_spdy_module, potentially resulting in arbitrary code
    execution (CVE-2014-0133).
    Thanks to Lucas Molas, researcher at Programa STIC, Fundación Dr.
    Manuel Sadosky, Buenos Aires, Argentina.

 Changeset: http://hg.nginx.org/nginx/rev/e7f7d30196e3

 Note that this bug has been fixed in Tengine-2.0.2.

 *) Bugfix: in the "fastcgi_next_upstream" directive.
    Thanks to Lucas Molas.

 Changeset: http://hg.nginx.org/nginx/rev/b246018860a2
Merge pull request #438 from chobits/nginx-update-1.4.7

merge changes between nginx 1.4.6 and 1.4.7