Update from 1.7.5 to 1.7.6.

<ChangeLog>

*) Change: the deprecated "limit_zone" directive is not supported

anymore.

*) Feature: the "limit_conn_zone" and "limit_req_zone" directives now

can be used with combinations of multiple variables.

*) Bugfix: request body might be transmitted incorrectly when retrying a

FastCGI request to the next upstream server.

*) Bugfix: in logging to syslog.

</ChangeLog>