libselinux: new package

[Thomas:
  - Add hash file.
  - Enable on all architectures, and enable on uClibc. The
    autobuilders will let us know if there are any problems.
  - Use "Public Domain" as the license instead of "PublicDomain"
  - Handle Python 2 vs. Python 3 for the host package. Either can be
    used by libselinux.
  - Change the trick used to get the library and programs installed in
    usr/lib/ and usr/sbin/ instead of lib/ and sbin/.]

Signed-off-by: Matt Weber <matthew.weber@rockwellcollins.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>