plan: add freebsd-asl porting plan

Companion to launchd/configd/kmodloader. Ports Apple's ASL (Apple
System Logger; APSL 2.0; latest tag syslog-97.1 at apple-oss-distributions/
syslog) as a launchd-supervised replacement for FreeBSD's /usr/sbin/syslogd.

Drops Mach IPC (replaced by GNUstep Distributed Objects over AF_UNIX,
same pattern as the configd port). Drops iOS/sim variants, AirPort/
SecurityFoundation integration. Keeps Apple's bsd_out.c so existing
FreeBSD admin tooling (tail /var/log/messages, grep, etc.) keeps
working unchanged — the ASL syslogd writes BOTH the binary asl store
AND the conventional BSD text files.

Lives in the monorepo under asl/ at the top of freebsd-launchd
(matching configd/, kmodloader/). Phase 6+ work — well after the
launchd port stabilizes and configd ships. The launchd port already
runs on plain BSD syslog; ASL is an upgrade path for structured
queries (filter by Sender/Facility/PID/Time without grep tricks).

License nuance: APSL 2.0 (not Apache 2.0 like launchd/configd) — Apple
specifically uses APSL for syslog. FSF-approved free software,
not GPL-compatible. Per-file headers preserved on Apple-derived
files; top-level repo stays BSD-2-Clause.

Author: pkgdemon