Revise hostkeys@openssh.com hostkey learning extension.
The client will not ask the server to prove ownership of the private
halves of any hitherto-unseen hostkeys it offers to the client.
Allow UpdateHostKeys option to take an 'ask' argument to let the
user manually review keys offered.
ok markus@
[bufaux.c bufbn.c bufec.c buffer.c buffer.h sshbuf-getput-basic.c]
[sshbuf-getput-crypto.c sshbuf-misc.c sshbuf.c sshbuf.h ssherr.c]
[ssherr.h]
New buffer API; the first installment of the conversion/replacement
of OpenSSH's internals to make them usable as a standalone library.
This includes a set of wrappers to make it compatible with the
existing buffer API so replacement can occur incrementally.
With and ok markus@
Thanks also to Ben Hawkes, David Tomaschik, Ivan Fratric, Matthew
Dempsky and Ron Bowes for a detailed review.