rc-status: fix -a to show all services

We need to unset rc_svcname so that all of the services are added to the
list to display.

X-Gentoo-Bug: 409787
X-Gentoo-Bug-URL: https://bugs.gentoo.org/show_bug.cgi?id=409787
typo fix

X-Gentoo-Bug: 477006
X-Gentoo-Bug-URL: https://bugs.gentoo.org/show_bug.cgi?id=477006
rc-status: fix typo

X-Gentoo-Bug: 477318
X-Gentoo-Bug-URL: https://bugs.gentoo.org/show_bug.cgi?id=477318
tmpfiles: make b and c commands set ownership and permissions

The b and c commands in tmpfiles.sh were not setting ownership and
permissions for the device nodes.
tmpfiles: add --prefix and --exclude-prefix options
Introduce the tmpfiles.dev service

This service handles setting up the tmpfiles entries for the /dev
directory for Linux systems which needs to be run in the sysinit
runlevel.
rc-cgroup: make sure the tasks file exists before adding the pid
Add support for DragonFly BSD
swapfiles: do not try to unmount all tmpfs mounts

This is handled in the swap script, so it should not be done here as
well.

X-Gentoo-Bug: 477534
X-Gentoo-Bug-URL: https://bugs.gentoo.org/show_bug.cgi?id=477534
tmpfiles: do not signal an error if device nodes already exist

X-Gentoo-Bug: 478336
X-Gentoo-Bug-URL: https://bugs.gentoo.org/show_bug.cgi?id=478336