add sock_test module and some basic initial tests

rename irc_nm to irc_proto, and move numerics from irc_cmd.h

implement irc_chan_callbacks, and add on_msg

change irc_chan.state into bool fields, move irc_cmd implementation from irc_conn.c into irc_cmd.c, remove irc_conn arg from irc_cmd_handler, add irc_conn.nickname tracking, and handle irc_chan JOINs

add irc_prefix_* functions to parse nicknames (plus sketch out some irc_nickmask stuff)

add a kind of semi-generic chain-list implementation

add doxygen.conf, and tweak comments

add line_proto_callbacks.on_error, although irc_conn doesn't pass it up

convert line_proto to use a line_proto_callbacks struct

error.c formatting