Do not use deprecated flask.h and av_permissions.h
    
    selinux/flask.h and selinux/av_permissions.h will be completely dropped in the
    next SELinux release.
    
    Use string_to_security_class() and string_to_av_perm() to get class and
    permission values. The original hardcoded values could be invalid and are
    deprecated as the whole flask.h and av_permissions.h header files.
    
    Fixes: https://pagure.io/libuser/issue/44