sound/mpd: update to mpd 0.16.8

updating to latest mpd requres more work on dependencies
(libmms,libaudiofile,libstdcpp)

- mpd isn't hosted on sourceforge anymore

- fix: https://dev.openwrt.org/ticket/14422
Issue 1: could not replicate
Issue 2: update to last mpd 0.16 series fixes compile,
its linked to ffmpeg version

Signed-off-by: Dirk Neukirchen <dirkneukirchen@web.de>