[PATCH 0 of 1] Upstream: add propagate_connection_close directive

[Shawn J. Goff]

This patch adds a new directive to the upstream module:
propagate_connection_close. It puts a "Connection: close" header in
the downstream response if the upstream server sent one. This is
useful when Nginx is used as HTTP/HTTPS endpoints with load blancers
in front of them. It allows the upstream server to close connections
in order to shed load.

I can submit a documentation patch if this patch is accepted.

In addition to being useful for us, I've found several examples of
people asking for this type of behavior in public forums.
https://github.com/openresty/headers-more-nginx-module/issues/22
http://stackoverflow.com/questions/5100971/nginx-and-proxy-pass-send-connection-close-headers
http://serverfault.com/questions/480171/is-it-possible-to-tell-nginx-over-fastcgi-to-pass-a-connection-close-header-thr