nginx版本更新到0.8.50

Changes with nginx 0.8.50                                        02 Sep 2010

    *) Feature: the "secure_link", "secure_link_md5", and
       "secure_link_expires" directives of the ngx_http_secure_link_module.

    *) Feature: the -q switch.
       Thanks to Gena Makhomed.

    *) Bugfix: worker processes may got caught in an endless loop during
       reconfiguration, if a caching was used; the bug had appeared in
       0.8.48.

    *) Bugfix: in the "gzip_disable" directive.
       Thanks to Derrick Petzold.

    *) Bugfix: nginx/Windows could not send stop, quit, reopen, and reload
       signals to a process run in other session.