vbox: Introduce IVirtualBoxErrorInfo interface

vbox: Introduce IVirtualBoxErrorInfo interface

The IVirtualBoxErrorInfo interface allows us to query error
messages from VirtualBox. Since VirtualBox has stacked errors we
need the GetNext() method too.

The odd one, that sticks out is GetIID() as it is not part of the
interface as defined by VirtualBox header files. BUT, we need to
get the interface UUID (which MAY change across each release) so
that it can be passed to VBOX_QUERY_INTERFACE() introduced
earlier.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Martin Kletzander <mkletzan@redhat.com>