Turn on loadable modules for libvirtd. Add new sub-RPMs
libvirt-daemon-driver-XXX, one for each loadable .so.
Modify the libvirt-daemon-YYY RPMs to depend on each of
the individual drivers they required

* libvirt.spec.in: Enable driver modules
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>