encryption state here, that is already done by
make_ssh_connection.
(do_fail): Replace with a definition that uses
DEFINE_PACKET_HANDLER.
(do_unimplemented): Likewise.
(connection_ignore_handler): Moved handler from packet_ignore.c,
and made it static.
(connection_forward_handler): New handler.
(make_ssh_connection): Updated initialization to use static
handlers.

Rev: src/connection.c:1.58