Two additional user groups - Banned & Custom

Addition of two extra user groups, a Banned group which is treated the
same as an individual chat ban, except the ban does not expire, plus a
Custom user group which is treated the same as the standard
AJAX_CHAT_USER group. What good is this for? Well maybe you want to
distinguish a special group of chatters from the rest with their own
username colour - e.g. top contributors, help team, 'paid' membership
perks...

Use of both the banned and custom groups is configured via your forum's
specific CustomAJAXChat.php file.