This patch should continue to allow mpd to play as well as
possible to icecast servers while avoiding stalls on local
devices.  This has eliminated ALSA underrun errors
for me while streaming to a remote host while the network
connection was bad.

Of course, this makes opening a connection non-blocking, too,
so myShout_openShoutConn is a bit more complex.

git-svn-id: https://svn.musicpd.org/mpd/trunk@4898 09075e82-0dd4-0310-85a5-a0d7c8717e4f