The private global variable nghttp2_enable_strict_preface is also
marked as NGHTTP2_EXTERN, but it is test purpose only (test with
.dll), and not part of public API.  It could be removed in the future
release.

This commit makes sure that WebSocket upgrade works for HTTP/1.1
frontend and backend pair.  Actually, this implementation probably
supports other upgrade as well, other than HTTP/2 Upgrade, which is
handled specially in other place.

Setting TCP_NODELAY may fail. Instead of failing the routine, log it and continue.
It seems, that setting TCP_NODELAY in python on Mac OS X is not necessarily supported.

Use the example presented at
http://en.wikibooks.org/wiki/OpenSSL/Initialization

Official golang spdy package is done.  We made a copy of it until we
drop spdy support.

We may log before filling scheme in Downstream, so we leave
construct_absolute_request_uri as is.

This uninstall-local rule is too strong; it could delete unexpected
files, although they are likely nghttp2 related.