Modified behaviour of method 'found'

I expected method `found` to return a list of files that *already have been found* instead of a list of files that "have been or are found when the method is called". Calling `found` with the existing implementation may croak on reading errors. Calling  `found` with the modified code is safe. This pull request slightly changes backwards compatibility, but the documentation does not say that method `found` may also load files.