Multi-threaded directory recurser function done

This function will enter a directory and fork off processes that will
simultaneously process all content in that directory.

Now, this only really expects to find all FLAC files at the second
directory level, so this may cause issues if you have FLAC files at
different levels. In that case, may be forking may not be a great
idea...
User-facing part for script done

The user-facing part will process input arguments and pass on each input
to the processing function. This script can now handle multiple
arguments, a mix of files and directories, with and without spaces in
the names.
Minor formatting changes