Upstream: u->conf->preserve_output flag. The flag can be used to continue sending request body even after we've got a response from the backend. In particular, this is needed for gRPC proxying of bidirectional streaming RPCs, and also to send control frames in other forms of RPCs.

make -f misc/GNUmakefile release

the required tools:
*) xsltproc to build CHANGES,
*) xslscript.pl ( http://hg.nginx.org/xslscript ) to build XSLTs
   from XSLScript sources.


make -f misc/GNUmakefile icons

the required tool:
*) netpbm to create Win32 icons from xpm sources.