machine and session ID

[Havoc Pennington <hp redhat com>]

Hi,

For those who don't know, dbus 1.0 has a GUID for the host, and dbus 1.1 
(soon to be 1.2) has a GUID for the session also (dbus_bus_get_guid()).

These may be useful on occasion. My belief is that "the session" should 
be defined as "the set of things using the same session bus" and thus 
the dbus session bus GUID is a unique identifier for the session.

If it's helpful, we could have dbus-launch set the session GUID in an 
environment variable also.

Havoc