runscript used to dlopen() runscript_selinux.so. This adds equivalent
functionality directly in to runscript instead. It authenticates with
either PAM or shadow and optionally has a dep on audit.
X-Gentoo-Bug: 517450
X-Gentoo-Bug-URL: https://bugs.gentoo.org/show_bug.cgi?id=517450
This allows error checking inside the included files instead of either
including the appropriate file or a blank file.
Also the blank file named .mk gets removed by this change.
