This function is used to send "error messages", including numerics,
back to clients and to automatically enforce a 2 second penalty. With
this patch, all error results enforces a delay for the client.
All callers of IRC_WriteStrClient(ERR_xxx) have been converted.
Please note that this patch prolongs the time "make check" needs
to complete its tests, because of lots of new enforced penalties ...
Now ngIRCd is able to handle "CAP LS", "CAP REQ", "CAP LIST", and
"CAP CLEAR" commands.
"multi-prefix" can be set/unset, but has no functionality - yet!
This patch implements the core functions to support "IRC Capabilities"
and the IRC "CAP" command as used by other servers and specified here:
<http://www.leeh.co.uk/draft-mitchell-irc-capabilities-02.html>.
It enables ngIRCd to support the defined handshake, but it doesn't
implement any capabilities, so "CAP LS" and "CAP LIST" always return
the empty set and "CAP REQ ..." always fails with "CAP NAK".