I embed cow_uri since I can't update Cowlib further easily.
This is most likely a one shot release so it shouldn't be
a problem to do things a little more dirty than usual.

If cowboy_static is initialized with `{priv_file, ...}` or `{priv_dir,
...}`, it is now able to read files from Erlang application .ez
archives.

When serving a file from an archive, the #file_info{} comes from the
archive, not the contained file, except for the size and type. The
erl_prim_loader module is used to read the latter's #file_info{} and the
actual file content (ie. sendfile(2) is not used in this case).

(cherry picked from commit 2166733628bbab0eb77eeed58bdf204727c48ec6)

Backported from Cowlib's patch from Rob Ashton <robashton@codeofrob.com>.

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.