Set channel mode flags for channel on
server connected to by connection. Mode flags
are passed in mode_spec and are applied to
the user specified by nick.
connectionA connection resource handle returned by ircg_pconnect().
channelThe channel name as #name.
mode_spec
The mode to be applied on nick.
Mode flags are set or cleared by specifying a mode character and
prepending it with a plus or minus character,
respectively. E.g. operator mode is granted by '+o' and revoked
by '-o', as passed as mode_spec.
nickThe user on which to apply the given mode.