nginx undocumented directives

[Yaroslav Zhuravlev]

Hello! 

[…]

>> But directive subrequest_output_buffer_size is still undocumented.
>> 
>> It is added by http://hg.nginx.org/nginx/rev/20f139e9ffa8#l4.7
>> 
>> It is undocumented by mistake (and will be documented in near future)
>> or it is undocumented by purpose and it will be never documented ?
>> 
> It is wip.

Documentation added for subrequest_output_buffer_size:

http://nginx.org/en/docs/http/ngx_http_core_module.html#subrequest_output_buffer_size
http://nginx.org/ru/docs/http/ngx_http_core_module.html#subrequest_output_buffer_size