Co-authored-by: Juhani Krekelä <juhani@krekelä.fi>

Co-authored-by: Meisaka Yukara <Meisaka.Yukara@gmail.com>

This change adds all the kernel parts of a network stack. The network stack
is partial but implements many of the important parts.

Add if(4) network interface abstraction. Network interfaces are registered
in a global list that can be iterated and each assigned an unique integer
identifier.

Add reference counted packets with a cache that recycles recent packets.

Add support for lo(4) loopback and ether(4) ethernet network interfaces.
The /dev/lo0 loopback device is created automatically on boot.

Add arp(4) address resolution protocol driver for translation of inet(4)
network layer addresses into ether(4) link layer addresses. arp(4) entries
are cached and evicted from the cache when needed or when the entry has not
been used for a while. The cache is limited to 256 entries for now.

Add ip(4) internet protocol version 4 support. IP fragmentation and options
are not implemented yet.

Add tcp(4) transmission control protocol sockets for a reliable transport
layer protocol that prov...

The futex and kutex implementations used the same linked list for waiting,
however the futex implementation used kutexs and the same thread could be in
the same list twice in the case of contention. This case corrupted the wait
lists and led to deadlocks and lost wakeups. This change fixes the problem
by having separate data structures for futexes and kutexes.

Mutexes contended by multiple threads could lead to lost wakeups since only
one contended thread was awoken and subsequent unlocks are unaware of the
unawakened contended threads. This change fixes the problem with a temporary
solution of waking all the contended threads until a better design is
implemented.

Additional details are tweaked to be more reliable and simpler.

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.