rmic should check that arguments and returns are correct for remote methods.

ok (interface extends java.rmi.Remote)
   - any remote interface is ok.

bad (class implements java.rmi.Remote)
   - no class that implements Remote, should always be an interface that extends
     Remote. This should cover both returning the impl whether it extends
     UnicastRemoteObject or not.

ok (Class that doesn't implement java.rmi.Remote)
   - classes passed by copy, i.e., not remote objects