Do a better job of telling the user whether we're interpreting a
module or using an existing object file.

eg.

   Main> :load A
   Skipping  D                ( D.hs, D.o )
   Compiling C                ( C.hs, interpreted )
   Skipping  B                ( B.hs, B.o )
   Compiling Main             ( A.hs, interpreted )
   Main>