This copies code contributed to ngx_headers_more by @zhuizhuhaomeng
in openresty/headers-more-nginx-module@d502e41

I omitted the PCRE2-related build flag added in that same commit because
I do not understand the reason for that.

This copies code contributed to ngx_headers_more by @hnakamur in
openresty/headers-more-nginx-module@91eb0db

https://github.com/nginx/nginx/commit/00ef9ff5f03ce7e98ba64c3644da25e5a0d659fc

This fixes #9 and #8 by reading headers_out from the subrequest resposne
and copying them into the main request's headers_out.  Previously, the
direct assignment (shallow copy) produced the effect whereby no filters
that ran after the shib module could modify headers.

The reason for this appears to be linking inside the ngx_list
``headers`` inside the request option; suffice to say, this is a much
better approach.

This reverts commit f5bfd9ea.

This ensures that Nginx can still manipulate responses from
the Shibboleth authorizer.

This mostly follows the FastCGI Authorizer specification, with the
exception of the processing of the request and response bodies, and
variable naming.

See http://forum.nginx.org/read.php?2,238523,238523#msg-238523


for a lengthier discussion.

Signed-off-by: Luca Bruno <luca.bruno@rocket-internet.de>

Signed-off-by: Luca Bruno <luca.bruno@rocket-internet.de>

Signed-off-by: Luca Bruno <luca.bruno@rocket-internet.de>