implement signal_ignore using sigaction directly, without any libevent in between

implement module unloading, although module_destroy is currently never called

create irc_log_chan function to log a new irc_log_chan, and irc_log_chan_destroy to remove the added callbacks/command handlers

add FindEvsql/FindLibPQ cmake modules and irc_log.sql definition, and implement logging of JOIN, PART, MODE, TOPIC, KICK, PRIVMSG, NOTICE and OPEN messages

implement the SQL logs table and the INSERT-logging code for mod_irc_log

all options are now fully implemented

add --module support, and tweak irc_net docs

...remove empty src/irc_log.h header

start reworking option-parsing, but --module/--config is still unimplemented

merge build-cmake -> default