#139 libaudiofile support depends on obsolete audiofile-config

[fberger]

To add support for libaudiotfile, rezound's ./configure checks for the 'audiofile-config' script that has been a part of libaudiofile.

However that script is gone with libaudiofile >= 0.3.0. See https://github.com/mpruett/audiofile/commit/88b8d104c668df22de69c92a2399a77cfc2a5c0a

With libaudiofile >= 0.3.0 installed, rezound's ./configure now reports:

*** The audiofile-config script installed by the Audio File Library could
*** not be found. If the Audio File Library was installed in PREFIX, make
*** sure PREFIX/bin is in your path, or set the AUDIOFILE_CONFIG
*** environment variable to the full path to audiofile-config.

This can not easily be fixed, as audiofile-config is gone.

As a consequence, it will not be possible to load WAV files in rezound, which is a major annoyance.

Please update rezound's ./configure for libaudiofile >= 0.3.0.

Thanks,
fberger