Bug#713072: Preliminary, but fully working packaging for musl-0.9.10

[Kevin Bortis <pkgs@bortis.ch>]

https://github.com/wermut/musl
https://github.com/wermut/musl.git

Works currently with musl-0.9.10:
http://www.musl-libc.org/releases/musl-0.9.10.tar.gz