IRCClient now supports PRIVMSG and NOTICE messages that are not
addressed to the client's nick, nor to any channel the client is on.
An example is the AUTH messages that some servers emit at the start
of the connection process.

IRC_Numerics.plist contains a mapping of known IRC numeric message
codes (taken from https://www.alien.net.au/irc/irc2numerics.html) to
their ASCII names. This is mostly for internal dev/debugging use.

The IRCClientChannel 'name' property was readwrite. This is obviously
incorrect - you cannot change the name of a channel the user has joined,
so you shouldn't be able to change the object's name property!

IRCClient should no longer have any issues with null termination
of strings (expecting terminated strings and not getting them,
or vice versa).

IRCClientChannel and IRCClientSession had properties which were defined
and adorned with memory management keywords in contravention of best
practices and Apple recommendations. These have been rectified.

No API changes accompany this fix.