Add support for full-duplex streaming

[wpt-issue-mover]

Originally posted as w3c/wptserve#80 by @louiscryan on 25 Mar 2016, 19:49 UTC:

@annevk
@domenic

As discussed over on whatwg/fetch#229 in order to validate the now formalized support for full-duplex streaming in the WHATWG Fetch API we need to be able to test it.

One suggestion is to use hyper-h2 and implement an HTTP2 capable server that can be used for testing. @Lukasa & @tbetbetbe might be able to help out with that.

[wpt-issue-mover]

Originally posted as w3c/wptserve#80 (comment) by @Lukasa on 25 Mar 2016, 20:36 UTC:

There are some demonstrations of how to build a HTTP/2 capable server using hyper-h2 in the docs. The most fully-featured one is the example WSGI server, though that contains a lot of extra detail around the WSGI-handling logic that would be irrelevant for this situation.

If more specific advice would be useful let me know. =)

[Hexcles]

Duplicate of #7693