nginx 升级到 1.4.7，有安全补丁，推荐升级

Changes with nginx 1.4.7                                         18 Mar 2014

*) 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.

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