On x32, the size_t parameter may be passed in the lower 32 bits of a
64-bit register with the non-zero upper 32 bits.  The string/memory
functions written in assembly can only use the lower 32 bits of a
64-bit register as length or must clear the upper 32 bits before using
the full 64-bit register for length.

This pach fixes memrchr for x32.  Tested on x86-64 and x32.  On x86-64,
libc.so is the same with and withou the fix.

	[BZ# 24097]
	CVE-2019-6488
	* sysdeps/x86_64/memrchr.S: Use RDX_LP for length.
	* sysdeps/x86_64/multiarch/memrchr-avx2.S: Likewise.
	* sysdeps/x86_64/x32/Makefile (tests): Add tst-size_t-memrchr.
	* sysdeps/x86_64/x32/tst-size_t-memrchr.c: New file.

	* All files with FSF copyright notices: Update copyright dates
	using scripts/update-copyrights.
	* locale/programs/charmap-kw.h: Regenerated.
	* locale/programs/locfile-kw.h: Likewise.

	* All files with FSF copyright notices: Update copyright dates
	using scripts/update-copyrights.
	* locale/programs/charmap-kw.h: Regenerated.
	* locale/programs/locfile-kw.h: Likewise.

By x86-64 specification, 32-bit destination registers are zero-extended
to 64 bits.  There is no need to use 64-bit registers when only the lower
32 bits are non-zero.  Also 2 instructions in:

	mov	%rdi, %rcx
	and	$15, %rcx
	jz	L(length_less16_offset0)

	mov	%rdi, %rcx		<<< redundant
	and	$15, %rcx		<<< redundant

are redundant.

	* sysdeps/x86_64/memrchr.S (__memrchr): Use 32-bit registers for
	the lower 32 bits.  Remove redundant instructions.

On x86_64, memrchr (not a standard function) is defined as a strong
symbol, instead of a weak alias of __memrchr as on other
architectures.  This results in linknamespace test failures from the
use of __memrchr from dirname.  (Not a conformance issue because of
the mem* reservation, but contrary to glibc conventions.)  This patch
makes x86_64 follow other architectures by defining memrchr as a weak
alias.

Tested for x86_64 (testsuite, and that disassembly of installed shared
libraries is unchanged by the patch).

	[BZ #17719]
	* sysdeps/x86_64/memrchr.S (memrchr): Rename to __memrchr and
	define as weak alias of __memrchr.
	(__memrchr): Do not define as strong alias of memrchr.
	* conform/Makefile (test-xfail-XPG4/libgen.h/linknamespace):
	Remove variable.
	(test-xfail-UNIX98/libgen.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K/libgen.h/linknamespace): Likewise.
	(test-xfail-XOPEN2K8/libgen.h/linknamespace): Likewise.