Remove $FreeBSD$: one-line sh pattern

Remove /^\s*#[#!]?\s*\$FreeBSD\$.*$\n/

pkgbase: Put more binaries/lib in runtime

Move some needed binaries/libs from FreeBSD-utilities to FreeBSD_runtime.
This is everything needed to boot to multiuser with FreeBSD-rc installed.

MFC after: 2 weeks
Sponsored by: Beckhoff Automation GmbH & Co. KG
Differential Revision: https://reviews.freebsd.org/D33435

pkgbase: Remove FreeBSD-libregex package

The only user of libregex is grep (and its variation), no need for a
dedicated package.
This moves libregex to the default package (FreeBSD-utilities).

Differential Revision: https://reviews.freebsd.org/D31802

libregex: re-enable `make check`

The tests are generally expected to pass, uncomment the annotation that
lets `make check` work. Note that `make check` currently requires kyua
from ports or an appropriate symlink into /usr/local/bin.

libregex: Add a symbol map

kib points out that trying to re-use symbol versioning from libc is dirty
and wrong. The implementation in libregex is incompatible by design with the
implementation in libc. Using the symbol versions from libc can and likely
will cause confusions for linkers and bring unexpected behavior for
consumers that unwillingly (transitively) link against libregex.

Reported by: kib

libregex: Drop WARNS to 2 to match libc

It's become clear that my armv7 builds didn't catch all of the warnings that
other builds are picking up, drop WARNS to 2 to match libc until they're all
caught.

Add libregex, connect it to the build

libregex is a regex(3) implementation intended to feature GNU extensions and
any other non-POSIX compliant extensions that are deemed worthy.

These extensions are separated out into a separate library for the sake of
not cluttering up libc further with them as well as not deteriorating the
speed (or lack thereof) of the libc implementation.

libregex is implemented as a build of the libc implementation with LIBREGEX
defined to distinguish this from a libc build. The reasons for
implementation like this are two-fold:

1.) Maintenance- This reduces the overhead induced by adding yet another
regex implementation to base.

2.) Ease of use- Flipping on GNU extensions will be as simple as linking
against libregex, and POSIX-compliant compilations can be guaranteed with a
REG_POSIX cflag that should be ignored by libc/regex and disables extensions
in libregex. It is also easier to keep REG_POSIX sane and POSIX pure when
implemented in this fashion.

Tests are added for future functionality, but left disconnected for the time
being while other testing is done.

Reviewed by: cem (previous version)
Differential Revision: https://reviews.freebsd.org/D12934