illumos gate

Update set from FreeBSD. Support UEFI HTTPClient. If the DHCP HTTPClient Class is defined, and we return http url as filename property value, this code does implement access to files over http. The implementation is still basic but we can make this work available in illumos anyhow.

Patch list:
https://svnweb.freebsd.org/base?view=revision&revision=349349
https://svnweb.freebsd.org/base?view=revision&revision=349404
https://svnweb.freebsd.org/base?view=revision&revision=349564
https://svnweb.freebsd.org/base?view=revision&revision=349565
https://svnweb.freebsd.org/base?view=revision&revision=349566

and inital commit message:

    Add support for an HTTP "network filesystem" using the UEFI's HTTP
    stack.

    This also supports HTTPS, but TianoCore EDK2 implementations currently
    crash while fetching loader files.
    Only IPv4 is supported at the moment. IPv6 support is planned for a
    follow-up changeset.

    Note that we include some headers from the TianoCore EDK II project in
    stand/efi/include/Protocol verbatim, including links to the license instead
    of including the full text because that's their preferred way of
    communicating it, despite not being normal FreeBSD project practice.