Convert packet_send_debug and packet_disconnect from macros to
functions. Some older GCCs (2.7.x, 2.95.x) see to have problems with
variadic macros with only one argument so we convert these two into
functions. ok djm@
update packet.c & isolate, introduce struct ssh a) switch
packet.c to buffer api and isolate per-connection info into struct ssh b)
(de)serialization of the state is moved from monitor to packet.c c) the old
packet.c API is implemented in opacket.[ch] d) compress.c/h is removed and
integrated into packet.c with and ok djm@
