reply() used to require an event, but all it used it for was to
determine the destination and to identify recursion. basically, strictly
only -replies-. we can make this a more robust privmsg, too, by adding
explicit_target and inferring recursion as False. this will let
basically any code currently using privmsg to use reply instead, and
benefit from multi-line and line splitting
bss/dr.botzo#21