Remove extra debug that crept in

Implement pubkey support for the bootstrap

Note that to not interfer with finger print it expects a signature on pkg itself
which is named pkg.txz.pubkeysign

To genrate it:
echo -n "$(sha256 -q pkg.txz)" | openssl dgst -sha256 -sign /thekey \
    -binary -out ./pkg.txz.pubkeysig

Note the "echo -n" which prevent signing the '\n' one would get otherwise

PR:		202622

Issue warning and refuse to proceed further if the configured
repository signature_type is unsupported by bootstrap pkg(7).

Previously, when signature_type specified an unsupported method,
the bootstrap pkg(7) would proceed like when signature_type is
"none".  MITM attackers may be able to use this vulnerability and
bypass validation and install their own versions of pkg(8).

At this time, only fingerprint and none are supported by the
bootstrap pkg(7).

FreeBSD's official pkg(8) repository uses the fingerprint method
and is therefore unaffected.

Errata candidate.

Allow fetching pkg(8) even if servers/proxies are not passing Content-length

Remove spurious libelf dependency.

Submitted by:	pluknet

Use pkg-1.4-style platform identifiers based on MACHINE_ARCH (e.g.
FreeBSD:11:amd64 instead of freebsd:11:x86:64) when bootstrapping pkg.
Thanks to portmgr for providing symlinks so both styles work.

Reviewed by:	bapt
MFC after:	3 weeks

Do not print a question in non-interractive mode but explain why boostrapping
has failed and how to allow it to happen

Reported by:	jmmv

argc is now used

Remove useless checks for NULL pointer before free(3)

Reported by:		eadler
Approved by:		eadler

Remove condition which can never be true as the previous loop
is never exited while remote == NULL.