libnetwork: Synchronize netresolv with NetBSD 9.3.

Some of the Haiku-specific modifications that were previously unmarked
are now clearly marked with #ifdef __HAIKU__.

BIND9-specific files containing private APIs never exposed in public
headers have been removed.

Tested with wget, curl, pkgman (Network Kit), WebPositive (WebKit/curl),
and Falkon (QtWebEngine/Chromium). All DNS-related operations seem
to still work just fine.

(One patch also imported from NetBSD trunk for GCC 12+ compatibility.)

Change-Id: I4a349577b24b4df008fd9cba5d3a322cd24397f1
Reviewed-on: https://review.haiku-os.org/c/haiku/+/6879
Reviewed-by: waddlesplash <waddlesplash@gmail.com>

libnetwork: Remove lcl_sv.cpp.

This has not been included in the build for years, probably since the
initial NetResolv merge. Services are now returned via the "protocols"
file, and getservent() has no need for these utility functions.

Change-Id: If18bdd9593463b38a9aaedb7a621d0ddc15530e4
Reviewed-on: https://review.haiku-os.org/c/haiku/+/6878
Tested-by: Commit checker robot <no-reply+buildbot@haiku-os.org>
Reviewed-by: waddlesplash <waddlesplash@gmail.com>

libnetwork: Replace some basic inet_* functions with the musl versions.

This beings the replacement of the libbind/netresolv-based implementation
with musl's equivalent. The code is less well commented in some places,
but it is well-designed and well-maintained, and the licensing situation
is much cleaner than the multi-BSD-licensed libbind-derivative code,
as well as being actively maintained (supposedly NetBSD has taken over
libbind/netresolv, but have not posted any portable code since 2013.)

The eventual goal is to replace the entirety of NetResolv with code
from musl, which will be an involved process as ABI compatibility
will be a problem. These functions at least are extremely
straightforward to replace.

Change-Id: Icfefaa90cbf56b012e4e42360be5b0f0c16d73bf
Reviewed-on: https://review.haiku-os.org/c/haiku/+/2943
Reviewed-by: Alex von Gluck IV <kallisti5@unixzen.com>
Reviewed-by: Adrien Destugues <pulkomandy@gmail.com>
Reviewed-by: Axel Dörfler <axeld@pinc-software.de>

Add a features.h to auto enable _DEFAULT_SOURCE

Unless __STRICT_ANSI__ is defined (as it is when running the compiler in
--std=c89 or --std=c99, but not when running it without any specific
args), we can enable these by default and behave like most other
systems. I don't know why no one has done this yet despite suggesting it
multiple times and people prefer to #define _BSD_SOURCE manually
everywhere.

Remove all places in our Jamfiles and sources where it had been defined.
_DEFAULT_SOURCE is now enabled by default for all sources of Haiku, since we
let the compiler use GNU extensions (no strict C standard specified on
command line)

Use _DEFAULT_SOURCE as the define name to match current versions of
glibc. Enable it if _BSD_SOURCE is #defined in compiler flags, for
backward compatibility.

Change-Id: I6db04da5f6db437723cdfba3478f5094a69d7727
Reviewed-on: https://review.haiku-os.org/c/1633
Reviewed-by: Jérôme Duval <jerome.duval@gmail.com>

libnetwork: Move from src/kits to src/system.

Properly speaking, this is part of POSIX and not of the Be-style
"kits", and so it should live in system/ alongside libroot.
No functional change intended.

Change-Id: I0fcf78a09c76e220ad4f1719d147978ef4a3bc52
Reviewed-on: https://review.haiku-os.org/726
Reviewed-by: Axel Dörfler <axeld@pinc-software.de>
Reviewed-by: waddlesplash <waddlesplash@gmail.com>