Python wheels: including licenses for libsndfile dependencies

[threexc]

The libsndfile repo lists several different dependencies required, most of which are BSD-licensed:

sudo apt install autoconf autogen automake build-essential libasound2-dev \
  libflac-dev libogg-dev libtool libvorbis-dev libopus-dev libmp3lame-dev \
  libmpg123-dev pkg-config python

Specifically:

libasound2-dev: LGPL-2.1+
libflac-dev: GPL-2+ or LGPL-2.1+
libmp3lame-dev: Various (LGPL-2+)
libmpg123-dev: LGPL 2.1
libogg-dev: BSD-3-Clause
libopus-dev: BSD-3-Clause
libvorbis-dev: BSD-3-Clause

Since there's some linking going on, I think the wheels need to include license information for these projects. Would a PR to change this be helpful?

[bastibe]

We're linking dynamically to libsndfile, but we distribute libsndfile itself as a statically-linked library that includes all its dependencies.

A merge pull request would be greatly appreciated, to clarify this state of affairs.