This ReplayGain code is currently disabled because WavpackGetTagItem can't
seem to find replaygain_* fields in APEv2 tags (which is how wvgain stores
ReplayGain values).  Additionally, because APEv2 tags are stored at the end
of the file, this code is only implemented for regular files and not HTTP
streams.  Using HTTP seeking it *may* be possible to implement it for both.

git-svn-id: https://svn.musicpd.org/mpd/trunk@6656 09075e82-0dd4-0310-85a5-a0d7c8717e4f