We redirect stdin to /dev/null to work around a libao bug, but
this bug has been fixed in libao since 2003 (according to jat).

However, there are likely other bugs in other libraries (and
even our code!) that handle fd=0 incorrectly and I'd rather not
take the risk[1].  So So it's easiest to just keep
fd=0==/dev/null for now...

[1] - I've seen several of these myself...

git-svn-id: https://svn.musicpd.org/mpd/trunk@6849 09075e82-0dd4-0310-85a5-a0d7c8717e4f