Remove support for pre-authentication compression. Doing compression
early in the protocol probably seemed reasonable in the 1990s, but
today it's clearly a bad idea in terms of both cryptography (cf.
multiple compression oracle attacks in TLS) and attack surface.

Moreover, to support it across privilege-separation zlib needed
the assistance of a complex shared-memory manager that made the
required attack surface considerably larger.

Prompted by Guido Vranken pointing out a compiler-elided security
check in the shared memory manager found by Stack
(http://css.csail.mit.edu/stack/); ok deraadt@ markus@

NB. pre-auth authentication has been disabled by default in sshd
for >10 years.
dump_cfg_oct(ServerOpCodes code, int val)
{
	printf("%s 0%o\n", lookup_opcode_name(code), val);
}

dump_cfg_oct(ServerOpCodes code, int val)
{
	printf("%s 0%o\n", lookup_opcode_name(code), val);
}
