* automake.mk: Add new file.
* bugs/overwrite-input-file.sh: New test.
* file-name.c (create_stream): New function.
* por-file-writer.c (pfm_open_writer): Use fh_open to open the
file handle before creating the file, to ensure that we don't
truncate a file that we're reading. Make code easier to read by
using create_stream.