Update from 1.17.6 to 1.17.7.

<ChangeLog>

*) Bugfix: a segmentation fault might occur on start or during

reconfiguration if the "rewrite" directive with an empty replacement
string was used in the configuration.

*) Bugfix: a segmentation fault might occur in a worker process if the

"break" directive was used with the "alias" directive or with the
"proxy_pass" directive with a URI.

*) Bugfix: the "Location" response header line might contain garbage if

the request URI was rewritten to the one containing a null character.

*) Bugfix: requests with bodies were handled incorrectly when returning

redirections with the "error_page" directive; the bug had appeared in
0.7.12.

*) Bugfix: socket leak when using HTTP/2.

*) Bugfix: a timeout might occur while handling pipelined requests in an

SSL connection; the bug had appeared in 1.17.5.

*) Bugfix: in the ngx_http_dav_module.

</ChangeLog>