re-implement the finder using information from the driver.  The Finder
now has type

	ModuleName -> IO (Maybe (Module, ModuleLocation)

where
	data ModuleLocation  = ModuleLocation {
				hs_file  :: FilePath,
				hi_file  :: FilePath,
				obj_file :: FilePath
			      }

For a module in another package, the hs_file and obj_file components
are undefined.