Use unique filenames for temporary files in tests.

Thanks to Giovanni Mascellani for pointing out this problem.

http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=687405
Open files in binary mode on Windows.
Add support for building without documentation.
Validate compressed audio formats.
Fix null checks in afGetSampleFormat() and afGetVirtualSampleFormat().

Thanks to David Lassonde for pointing out this problem.
Fix conversion specifications in error messages.
Use C++11 override keyword with compilers that support it.
Include <unistd.h> to provide declaration of close().
Set compression type before initializing sample format.
Remove unnecessary check for positive channel count.

This check is already performed in afInitChannels().
Add test for opening a NeXT sound file with zero channels.
Report error when attempting to open a file with zero channels.
Report error when attempting to open a file with invalid sample width.
Update PCMData test to create multi-channel audio files.
Fix calculation of IRCAM frame size.
Remove test coverage files when cleaning.