sh/tmpfiles: tmpfiles.d support.

This is the baseline support for tmpfiles.d.

Still missing:
- SELinux relabel, pending upstream clarification
- LIBDIR vs multilib systems, pending upstream clarification
- Whitespace in paths?
- Clean support not implemented
- "x" exclude type not implemented

X-Gentoo-Bug: 396003
X-Gentoo-Bug-URL: https://bugs.gentoo.org/show_bug.cgi?id=396003
Signed-off-by: Robin H. Johnson <robbat2@gentoo.org>

sh/.gitignore

@@ -9,3 +9,4 @@ init-early.sh
 ifwatchd-carrier.sh
 ifwatchd-nocarrier.sh
 udhcpc-hook.sh
+tmpfiles.sh