That attribute was uninitialized before, which could crash
libavformat.

See Debian bug 760669

Log call was added to the wrong branch.

Fixes regression by commit ca1a1149

Simply return an empty WritableBuffer, not a nulled one.

The unit of gme_info_t::length is milliseconds, not centiseconds.

For type safety and code readability.

After seeking, the MPD core automatically refreshes the timestamp, and
thus discards the value from decoder_timestamp().

Avoid roundtrips to floating point.

Move to fixed-point integers instead of floating point.