libshairplay: new package

libshairplay is a client library that emulates an airplay server
This package was originally found at : https://github.com/huceke/buildroot-rbp


By gimli <ebsi4711@gmail.com>

[Peter: fix whitespace, needs threads, host-pkgconf and optionally libao]
Signed-off-by: Maxime Hadjinlian <maxime.hadjinlian@gmail.com>
Cc: gimli <ebsi4711@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>