Changes with nginx 0.6.18 27 Nov 2007

    *) Change: now the ngx_http_userid_module adds start time microseconds
       to the cookie field contains a pid value.

    *) Change: now the full request line instead of URI only is written to
       error_log.

    *) Feature: variables support in the "proxy_pass" directive.

    *) Feature: the "resolver" and "resolver_timeout" directives.

    *) Feature: now the directive "add_header last-modified ''" deletes a
       "Last-Modified" response header line.

    *) Bugfix: the "limit_rate" directive did not allow to use full
       throughput, even if limit value was very high.