9.31: the server ->cmode_string_difference() method now takes an argument
$remove_none which indicates that no modes should be unset. this was
previously not necessary for JELP because the servers burst one-at-a-time.
message parameter modifiers that are protocol-independent such as -msg,
-command, etc. now are provided by the message class rather and no longer
are required for each protocol implementation.
all outgoing command subroutines now have the message object rather than the
event fire object as their second argument.
the fire object can be retrieved through $msg->event.
added methods to message objects that aid the forwarding of translated
messages from one protocol to another:
$msg->forward:      forward a message to all servers but the source;
$msg->forward_to:   forward a message to a specific server.
added new forwarding logic to TS6 commands EUID and SJOIN.
renamed outgoing event uid -> new_user.
added new outgoing event create_channel for CUM/SJOIN
(new channel, not necessarily during burst).