InspIRCd: Don't reply to VERSION

InspIRCd sends all known version strings at burst and remembers the version strings sent to it. When a client does a /version <server> the cached version string is sent.
Check that channels still exist before nulling their ci pointer in channelinfos destructor
Change the persist setting on a channel to mean only that it is being
enforced ircd-side
Merge pull request #13 from attilamolnar/1.9+inspversionfix

InspIRCd: Don't reply to VERSION