Upstream: handling of proxy_set_header at http level. When headers are set at the "http" level and not redefined in a server block, we now preserve conf->headers into the "http" section configuration to inherit it to all servers. The same applies to conf->headers_cache, though it may not be effective if no servers use cache at the "server" level as conf->headers_cache is only initialized if cache is enabled on a given level. Similar changes made in fastcgi/scgi/uwsgi to preserve conf->params and conf->params_cache.