Use current attribute for -CURRENT manual pages. It is now possible to
make the difference between -STABLE and -CURRENT manual pages. We need
this for devfs, device.hints etc. manual pages in our Handbook.

Manual pages entities for -CURRENT should have the form &man.current.foo.1;
Note, this does not concern release notes but only docs.

An "old" man.devfs.5 entity is kept to allow the build of localized docs
till their upgrade.