This is to allow us to get useful information on messaging without being overwhelmed by the rest of groups debug.
Enabled with [Groups] DebugMessagingEnabled = true in config (default false)
Or "debug groups messaging verbose true|false on the console" (similar to existing groups setting).
Done for both xmlrpc and V2 groups.
This is because xmlrpcgroups currently always checks visibility for the requesting agent ID (unlike Groups v2, which can accept UUID.Zero)
But group notice IMs have a from agent which is the group rather than the sending agent.
Further addresses http://opensimulator.org/mantis/view.php?id=7037
The major departure from flotsam is to send only one message per destination region, as opposed to one message per group member. This reduces messaging considerably in large groups that have clusters of members in certain regions.
