This patch is based on a improvement suggested by Kazuhiro Kikuchi
of Fujitsu, it gives a description of the target parameter for that
command
* tools/virsh.pod: add description for target parameter of
attach-interface
I<model> allows to specify the model type.
I<persistent> indicates the changes will affect the next boot of the domain.
+B<Note>: the optional target value is the name of a device to be created
+as the back-end on the node. If not provided a device named "vnetN" or "vifN"
+will be created automatically.
+
=item B<detach-device> I<domain-id> I<FILE>
Detach a device from the domain, takes the same kind of XML descriptions