Fixes #839 when 'Connection: Keep-Alive' wasn't sent in a HTTP/1.0
response. Now the usage of 'Connection' header is consistent with
current protocol version: when this header is not specified explicitly
in the response, HTTP/1.0 implies 'Connection: close' and HTTP/1.1
implies 'Connection: Keep-Alive'. So if current 'Connection' value
matches the default value of current protocol, we won't state obvious
fact in the response; and vice versa.

Amended to fix and improve tests, and revert the variable name
change from HTTP11Headers to StdHeaders. I think it's still good
to leave it as is because it's not really a standard header for
HTTP/1.0, and it's gone from HTTP/2 entirely.

Mostly useful for REST, which has a ton. This is an initial
commit, it still needs to be tested, but it's time to sleep.

Yes I know the function never returns. :-)

Avoids unnecessary calculations.

Everything is now directly generated from the Makefile.
Also properly update dependencies.

Ah, conference commits.

This commit is not only an early preview of HTTP/2, it is an
early preview of the new Cowboy architecture that will be
presented tomorrow in my talk. If you have found it before
the talk, great! It's not complete so you better go watch
the talk anyway.