Build the policy interface database with 'sepolgen-ifgen'.
This database is required for reference style policy generation by
'audit2allow --reference'

Signed-off-by: Christian Göttsche <cgzones@googlemail.com>

Closes #100

Add this to all Travis-CI builds.

add the string values for the UNK_PERMS options
document SYSTEMD option

This support was deprecated and unused in Reference Policy November 5 2008.