So imagine you want to crate new security manager:

  if (!(mgr = virSecurityManagerNew("selinux", "QEMU", false, true, false, true)));

Hard to parse, right? What about this:

  if (!(mgr = virSecurityManagerNew("selinux", "QEMU",
                                    VIR_SECURITY_MANAGER_DEFAULT_CONFINED |
                                    VIR_SECURITY_MANAGER_PRIVILEGED)));

Now that's better! This is what the commit does.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>