This change implements a dependency tracking daemon(7) system in init with
overridable init(5) configuration, parallel startup, readiness signaling,
rotating logs, reliable stopping, and handling of leaked processes.

The /etc/init/target file is replaced by the new /etc/init/default per the
new init(5) format. The old configuration is migrated upon upgrade using an
upgrade hook.

extfs(8) now signals readiness using READYFD for fast mounting.

Filesystems that fail to be repaired are now mounted read-only.

The mounting and filesystem checking code is synchronized with sysinstall.

The duplicated array_add utility function now protects against overflows.

tix-iso-bootconfig(8) gains the --init-target option.

tix-iso-liveconfig(8) gains the --daemons option.