io: add ability to set a name for IO channels

io: add ability to set a name for IO channels

The GSource object has ability to have a name, which is useful
when debugging performance problems with the mainloop event
callbacks that take too long. By associating a name with a
QIOChannel object, we can then set the name on any GSource
associated with the channel.

Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>