Add support for bracketed ipv6 address literals when generating URLs

    The format_s3_uri helper function calls http_uri:parse/2 and we now
    specify option {ipv6_host_with_brackets, true}. This gives us basic
    support for ipv6 address literals.

    Note that format_s3_uri supports both virtual host and path based
    bucket syntax. For IP addresses, the virtual host option returns a
    value, but one that won't work. If you're using IP addresses, you need
    to stick to type 'path'.

Also adding update of Makefiles via concrete.

/cc @marcparadise @manderson26 @hosh @oferrigni @sdelano