Fix incorrect handling of chroot option.
Fixes #28.

X-Gentoo-Bug: #527370
X-Gentoo-Bug-Url: https://bugs.gentoo.org/show_bug.cgi?id=527370
Integrate the functionality from runscript_selinux.so

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
netmount: unmount nfs file systems