Enable WHOIS to display information about IRC Services

This patch introduces the new numeric 310(RPL_WHOISSERVICE) and enables
WHOIS to display information about IRC services. This numeric is used
for this purpose by InspIRCd, for example -- but as usual, other numerics
are in use, too, like 613 in UltimateIRCd ...

Please note that neither the Operator (+o) not the "bot status" (+B)
of an IRC service id displayed in the output.

Change suggested by Federico G. Schwindt <fgsch@lodoss.net>, Thanks.
NewListener(): Code cleanup
Rename ports_initlisteners() to Init_Listeners()