Further I/O issues

As part of changing how file I/O is handled, it turns out I also need to convert from file pointers to file descriptors.  Unfortunately, all of the RIFF validation code is dependent on using file pointers.  I have successfully converted the rest of the code to use file descriptors, but I wont commit it until i have the basic RIFF things working again.  As it stands, the code will compile but segfaults upon trying to read the RIFF data. (I used fdopen to try to get around the issue, but this has been highly unsuccessful.)