strings.h: Fix visibility of bcmp/bcopy/bzero/index/rindex again.

These have always been X/Open / XSI options, and they were nixed in
POSIX 2008, not in POSIX 2024.

POSIX 2001 (marked legacy): https://pubs.opengroup.org/onlinepubs/009695399/basedefs/strings.h.html
POSIX 2008 (removed): https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/strings.h.html
POSIX 2024: https://pubs.opengroup.org/onlinepubs/9799919799.2024edition/functions/strcasecmp_l.html

Cleanup after fix for:

PR lib/58802: missing ffsl(), ffsll() functions from POSIX 2024

ffs(3): Fix visibility in strings.h and add MLINKS for ffsl/ffsll.

ffs(3) was added in POSIX 2001 with XSI option (_XOPEN_SOURCE>=600),
not in POSIX 2008 with XSI option (_XOPEN_SOURCE>=700).

Noticed while updating the STANDARDS section of the man page.

PR lib/58802: missing ffsl(), ffsll() functions from POSIX 2024

strings.h: Spruce up for POSIX 2024.

1. Add ffsl, ffsll.
2. Hide bcmp, bcopy, bzero, index, rindex for POSIX>=2024.
3. Expose ffs only for NetBSD or POSIX>=2008 with XSI option.
4. Hide popcount* NetBSD extensions for any POSIX.
5. Sprinkle __constfunc on ffs*.

Add tests for ffs/ffsl/ffsll in tests/include/sys/t_bitops next to
ffs32/ffs64 for convenience.

XXX Still missing strcasecmp_l, strncasecmp_l, and locale_t.

PR lib/58802: missing ffsl(), ffsll() functions from POSIX 2024

branches: 1.18.54;
Don't pollute the namespace with stdint.h. (This file is included from
string.h so it can't blithely do whatever it feels like.) PR 45258.

include <stdint.h> instead of <sys/types.h>.
the latter pulls FD_SET etc and it makes wine-1.1.27's winsock vs unixsocket
namespace dance unhappy. for more information, grep
Include_winsock_h_before_stdlib_h_or_use_the_MSVCRT_library
in their source.

Some parts of gcc fail with the direct include of sys/inttypes.h, so
fall back to using sys/types.h like stdlib.h does.

Move popcount et al to src/common and add popcount32/popcount64.
Requested by rmind@. MD should now override popcount32/popcount64 and
provide the aliases as fitting.

Add popcount(3) and the long and long long version. Name is inspired by
gnulib, the implementation goes back to the AMD Software Optimizer
guide. A number of platforms will want to replace the C version with
assembler code using native instructions.

branches: 1.13.10;
Remove clause 3 and 4 from TNF licenses

branches: 1.12.8; 1.12.10;
Do not include SSP files unless _FORTIFY_SOURCE > 0.

Match usage of FORTIFY_SOURCE on other platforms by not requiring special
include path: the normal header files now include the "SSP" ones (which one
should note are not really named right: SSP and FORTIFY_SOURCE are independent
features).

Disable USE_SSP on targets where the compiler doesn't support it at all
(mips, alpha) or it's known broken (sh3). But enable FORTIFY_SOURCE,
without SSP, on those platforms -- tested on mipsel.

branches: 1.10.10; 1.10.12;
de-__P -- the hack is long since useless. Discussed with christos,
matt, kleink, others. Approved by christos.

Add a new feature-test macro, _NETBSD_SOURCE. If this is defined
by the application, all NetBSD interfaces are made visible, even
if some other feature-test macro (like _POSIX_C_SOURCE) is defined.
<sys/featuretest.h> defined _NETBSD_SOURCE if none of _ANSI_SOURCE,
_POSIX_C_SOURCE and _XOPEN_SOURCE is defined, so as to preserve
existing behaviour.

This has two major advantages:
+ Programs that require non-POSIX facilities but define _POSIX_C_SOURCE
can trivially be overruled by putting -D_NETBSD_SOURCE in their CFLAGS.
+ It makes most of the #ifs simpler, in that they're all now ORs of the
various macros, rather than having checks for (!defined(_ANSI_SOURCE) ||
!defined(_POSIX_C_SOURCE) || !defined(_XOPEN_SOURCE)) all over the place.

I've tried not to change the semantics of the headers in any case where
_NETBSD_SOURCE wasn't defined, but there were some places where the
current semantics were clearly mad, and retaining them was harder than
correcting them. In particular, I've mostly normalised things so that
_ANSI_SOURCE gets you the smallest set of stuff, then _POSIX_C_SOURCE,
_XOPEN_SOURCE and _NETBSD_SOURCE in that order.

Tested by building for vax, encouraged by thorpej, and uncontested in
tech-userlevel for a week.

Move <null.h> to <sys/null.h> for the purpose of avoiding conflicts due to
std C headers including it, and a kernel module written in C++ would benfit
as well.

For the benefit of G++'s null pointer constant implementation, #define NULL
as __null with egcs 1.0 (GCC 2.90) and above. As several headers are affected
by this change, move the definition into a new header file, <null.h>, to ease
maintenance.

Don't make NULL available to _XOPEN_SOURCE.

If _XOPEN_SOURCE isn't defined, provide <string.h> definitions for
compatibility.

Rework this header to be XPG4.2-compliant: provide the symbols and prototypes
defined in the spec, and don't include the whole <string.h> header.

new RCS ID format.

Add RCS identifiers.

branches: 1.1.1;
Initial revision