Add package wavpack

WavPack is an open audio compression format that offers lossless,
lossy, and hybrid compression modes. (Hybrid mode: A lossily
compressed file is accompanied by a correction file that allows
lossless reconstruction of the original audio.) The library has a
three-clause BSD licence. Website: http://www.wavpack.com/

Built via autotools. No special dependencies; libiconv is only used
for the command-line programs, not for the library.
Build xine-lib with wavpack support

Activate wavpack support in xine-lib. This reveals a latent bug
(missing include) in xine-lib, for which a patch is provided.
Explicitly enable/disable dependencies for sox

Explicitly enable or disable all optional features of the sox package,
as recommended in the "Guidelines for Creating Packages". This ensures
a consistent build result.

FFmpeg is removed because libsox doesn't build against its current API
anyway, whether told so or not; cf. http://bugs.debian.org/693642
Build sox with wavpack support
Merge pull request #149 from uklauer/wavpack

Add package wavpack
package gst-plugins-good: add wavpack dependency
package sox: reformat configure options