sndfile is a sort-of lowest common denominator, which
makes it more appropriate as a default-on USE flag
than more desktop-oriented options such as ALSA.
Additionally, a test USE flag was added. When disabled,
tests are not run. Tests depend on sndfile.
Closes: https://bugs.gentoo.org/921846
Signed-off-by: Seth M. Price <sprice623@aol.com>
