Add timingsafe_bcmp and timingsafe_memcmp.

Obtained from:	OpenBSD
Reviewed by:	trasz

Fix strcoll_l disagreeing with strxfrm by reworking the forward order case in
wcscoll_l().

Illumos fixed this while grabbing back our patches:
https://www.illumos.org/rb/r/402/

This does not 100% fix what postgresql folks reported as there is still a
remaining issue: https://www.illumos.org/issues/7962, it improves the situation

The initial issue was reported in postgresql mailing lists:
https://www.postgresql.org/message-id/flat/111D0E27-A8F3-4A84-A4E0-B0FB703863DF@s24.com#111D0E27-A8F3-4A84-A4E0-B0FB703863DF@s24.com

Submitted by:	Yuri Pankov <yuri.pankov@nexenta.com>
Obtained from:	Illumos

Implement the memset_s(3) function as specified by the C11 ISO/IEC
9899:2011 Appendix K 3.7.4.1.

MFC r316258:
Only activate __EXT1_VISIBLE block when using sys/errno.h in userspace.

r312332:

Use SRCTOP where possible and use :H to manipulate .CURDIR to get rid of
unnecessarily long relative path .PATH values with make

r312446 (by emaste):

libc: remove reference to nonexistent lib/locale directory

As far as I can tell this was introduced in r72406 and updated in several
subsequent revisions, but the lib/locale directory it referenced never
existed.

r312451:

Replace dot-dot relative pathing with SRCTOP-relative paths where possible

This reduces build output, need for recalculating paths, and makes it clearer
which paths are relative to what areas in the source tree. The change in
performance over a locally mounted UFS filesystem was negligible in my testing,
but this may more positively impact other filesystems like NFS.

LIBC_SRCTOP was left alone so Juniper (and other users) can continue to
manipulate lib/libc/Makefile (and other Makefile.inc's under lib/libc) as
include Makefiles with custom options.

Discussed with:	marcel, sjg

Mostly on comments.

The rest of the manpage already referenced 'dstsize' but did not rename
the variable in the prototype in r257646.

MFC after:	3 days
Sponsored by:	EMC / Isilon Storage Division

Reviewed by:	cpercival
MFC after:	1 week

terminated.

If this buffer is adjacent to an unmapped page or a version of C with
bounds checked is used this may result in a crash.

PR:		206178
Submitted by:	Alexander Cherepanov <cherepan@mccme.ru>
MFC after:	1 week

terminated.

If this buffer is adjacent to an unmapped page or a version of C with
bounds checked is used this may result in a crash.

PR:		206177
Submitted by:	Alexander Cherepanov <cherepan@mccme.ru>
MFC after:	1 week

Through testing, the user noted that some Cyrillic characters were not
sorting correctly, and this was confirmed.

After extensive testing and review, the localedef tool was eliminated
as the culprit.  The sustitutions were encoded correctly in LC_COLLATE.

The error was mainly in wcscoll where character expansions were
mishandled.  The main directive pass routines had to be written to
go back for a new collation value when the "state" variable was set.
Before pointers were being advanced, the second lookup was gettting
applied to the wrong character, etc.

The "eat expansion codes" section on collate.c also had a bug.  Later
own, the "state" variable logic was changed to only set if next
code was greater than zero (rather than >= 0).

Some additional cleanups got captured from previous work:
1) The previous commit moved the binary search comment from the
   correct location to a wrong location because it's wrong upstream
   in Illumos.  The comment has little value so I just removed it.
2) Don't check if pointers are null before freeing, this is
   redundant as free() handles null pointers.
3) The two binary search trees were standardized wrt initialization
4) On the binary search trees, a negative "high" exits rather than
   checking the table count again.

Submitted by:	marino
Obtained from:	DragonflyBSD