Remove vde target, add monitor target, fix birth target

VDE switch setup should be up to the user, so I'm not going to put this
here. The monitor is now no longer accessible on stdout, but via Unix
socket. This allows having a monitor even though we do not have access
to stdio (e.g. when launched by a script).

The birth target (out of some reason) continued to have the 'M' suffix
for the size parameter. I hope it's now finally gone for good.