Zircon responds to various command line options and checks for various
environment variables. It also reads a preferences file which by
default lives in the file ~/.zircon/preferences (where ~ is your home
directory). Future versions of zircon will use the .zircon directory
for storing other configuration files etc. Environment variables have
take precedence over values set in the configuration file, and values
set on the command line take precedence over environment
variables. Before doing any of these, zircon will attempt to read the
system preferences file if it exists.

The environment variables used are:

	IRCNICK	: to set your nick
	IRCNAME	: to set your irc name
	IRCSERVER : to set the server to use
	(N.B. you can override the names of these variables by setting
	  zircon(envnick), zircon(envname) and zircon(envserver) in
	  your preferences file. This lets you have one set for other
	  clients and one for zircon)

	USER	: to find out your user name
	HOSTIPADDR : the IP address of your host (useful if you are on
		     a slip or PPP connection.
	ZIRCONPREFDIR : to set the name of the directory where the
			preferences file lives.