Revert "Based on email from Paulo Almeida, I removed the apparently extranous calls"

This reverts commit cd5ed1db59d1f93197fef72311e59cb42ed2ebc4.

Based on looking in the rest of file.ex and the foo and foo! methods,
they all use this same pattern. It's really kind of moot since
IO.char_to_string is almost always a single if_string return.

Either they should all be fixed, or they should all stay the same.

It might make sense to write a generalized bang macro.