There is no longer a need for string2.h, so remove it and all mention of it.
Move the redirect for __stpcpy to include/string.h since it is still required
until all internal uses have been renamed.
This fixes several linknamespace/localplt failures when building with -Os.

	[BZ #15105]
	[BZ #19463]
	* include/string.h: Add internal redirect for __stpcpy.
	* string/Makefile: Remove bits/string2.h.
	* string/string.h: Update comment.
	* string/string-inlines.c: Remove bits/string2.h include and comment.
	* string/bits/string2.h: Remove file.

calls with constant strings shows a small (~10%) performance gain, strdup is
typically used in error reporting code, so not performance critical.
Remove the now unused __need_malloc_and_calloc related defines from stdlib.h.

Rename existing uses of str(n)dup to __str(n)dup so it no longer needs to be
redirected to a builtin.  Also building GLIBC with -Os now no longer shows
localplt or linkname space failures (partial fix for BZ #15105 and BZ #19463).

        [BZ #15105]
        [BZ #19463]
        * elf/dl-cache.c (_dl_load_cache_lookup): Use __strdup.
        * inet/rcmd.c (rcmd_af): Likewise.
        * inet/rexec.c   (rexec_af): Likewise.
        * intl/dcigettext.c (_LIBC): Likewise.
        * intl/finddomain.c (_nl_find_domain): Use strdup expansion.
        * locale/loadarchive.c (_nl_load_locale_from_archive): Use __strdup.
        * locale/setlocale.c (setlocale): Likewise.
        * posix/spawn_faction_addopen.c
        (posix_spawn_file_actions_addopen): Likewise.
        * stdlib/putenv.c (putenv): Use __strndup.
        * sunrpc/svc_simple.c (__registerrpc): Use __strdup.
        * sysdeps/posix/getaddrinfo.c (gaih_inet): Use __strdup/__strndup.
        * include/stdlib.h (__need_malloc_and_calloc): Remove uses.
        (__Need_M_And_C) Remove define/undef.
        * stdlib/stdlib.h (__need_malloc_and_calloc): Remove uses.
        (__malloc_and_calloc_defined): Remove define.
        * string/bits/string2.h (__strdup): Remove define.
        (strdup): Likewise.
        (__strndup): Likewise.
        (strndup): Likewise.

optimization seems unlikely to ever be useful, but if it occurs in
real code it should be added to GCC.  Expanding strcmp of small strings
does appear useful (benchmarking shows it is 2-3x faster), so this would
be useful to implement in GCC (PR 78809).

	* string/bits/string2.h (strcmp): Remove define.
	(__strcmp_cg): Likewise.
	(strncmp): Likewise.

This is transformed into rawmemchr by the bits/string2.h header.
However this is generally slower than strlen on most targets, even when
an optimized rawmemchr implementation exists.  Since GCC7 optimizes
strchr (s, '\0') to strlen (s) + s, the GLIBC headers should not
transform this to rawmemchr.  As GCC recognizes strchr as a builtin,
defining strchr as the builtin is not useful.

	* string/bits/string2.h (strchr): Remove define.

Currently strsep calls strpbrk is is now a veneer to strcspn.  Calling
strcspn directly is faster.  Since it handles a delimiter string of size
1 as a special case, this is not needed in strsep itself.  Although this
means there is a slightly higher overhead if the delimiter size is 1,
all other cases are slightly faster.  The overall performance gain is 5-10%
on AArch64.

The string/bits/string2.h header contains optimizations for constant
delimiters of size 1-3.  Benchmarking these showed similar performance for
size 1 (since in all cases strchr/strchrnul is used), while size 2 and 3
can give up to 2x speedup for small input strings.  However if these cases
are common it seems much better to add this optimization to strcspn.
So move these header optimizations to string-inlines.c.

Improve the strsep benchmark so that it actually benchmarks something.
The current version contains a delimiter character at every position in the
input string, so there is very little work to do, and the extremely inefficent
simple_strsep implementation appears fastest in every case.  The new version
has either no match in the input for the fail case and a match halfway in the
input for the success case.  The input is then restored so that each iteration
does exactly the same amount of work.  Reduce the number of testcases since
simple_strsep takes a lot of time now.

	* benchtests/bench-strsep.c (oldstrsep): Add old implementation.
	(do_one_test) Restore original string so iteration works.
	* string/string-inlines.c (do_test): Create better input strings.
	(test_main) Reduce number of testruns.
	* string/string-inlines.c (__old_strsep_1c): New function.
	(__old_strsep_2c): Likewise.
	(__old_strsep_3c): Likewise.
	* string/strsep.c (__strsep): Remove case of small delim string.
	Call strcspn directly rather than strpbrk.
	* string/bits/string2.h (__strsep): Remove define.
	(__strsep_1c): Remove.
	(__strsep_2c): Remove.
	(__strsep_3c): Remove.
	(strsep): Remove.
	* sysdeps/unix/sysv/linux/internal_statvfs.c
	(__statvfs_getflags): Rename to __strsep.

calls strcspn, call strcspn directly so we get the end of the token without
an extra call to rawmemchr.  Also avoid an unnecessary call to strcspn after
the last token by adding an early exit for an empty string.  Change strtok
to tailcall strtok_r to avoid unnecessary code duplication.

Remove the special header optimization for strtok_r of a 1-character
constant string - both strspn and strcspn contain optimizations for this
case.  Benchmarking this showed similar performance in the worst case,
but up to 5.5x better performance in the "found" case for large inputs.

	* benchtests/bench-strtok.c (oldstrtok): Add old implementation.
	* string/strtok.c (strtok): Change to tailcall __strtok_r.
	* string/strtok_r.c (__strtok_r): Optimize for performance.
	* string/string-inlines.c (__old_strtok_r_1c): New function.
	* string/bits/string2.h (__strtok_r): Move to string-inlines.c.

The comment above the bzero() macro in this file appears to have been
copied verbatim from the comment above the memset() prototype in
string.h proper.  bzero() has no 'c' argument and can only set memory
contents to 0.  (The comment above the prototype of bzero() in
string.h proper does not make the same mistake.)

	* string/bits/string2.h: Fix typo in comment.

symbols as they are no longer used. Fix compat symbols for __strpbrk inlines.

        [BZ #18712]
        * string/string-inlines.c (__STRING2_COPY_TYPE): Add, moved from string2.h.
        (__old_mempcpy_small): Likewise.
        (__old_strcpy_small): Likewise.
        (__old_stpcpy_small): Likewise.
        (__old_strpbrk_c2): Fix compat symbol name.
        (__old_strpbrk_c3): Likewise.
        * string/bits/string2.h (__STRING2_COPY_TYPE): Remove.
        (__mempcpy_small): Remove.
        (__strcpy_small): Remove.
        (__stpcpy_small): Remove.

        * string/string.h: Use __GNUC_PREREQ(3,4) for bits/string2.h.
        * string/bits/string2.h (__STRING2_SMALL_GET16): Remove.
        (__STRING2_SMALL_GET32): Remove.
        (memset): Remove.
        (__memset_1): Remove.
        (__memset_gc): Remove.
        (__mempcpy): Remove.
        (mempcpy): Remove.
        (__mempcpy_args): Remove.
        (strchr): Remove.
        (strcpy): Remove.
        (strcpy_args): Remove.
        (__stpcpy_args): Remove.
        (__strcmp_cc): Remove.
        (__strcmp_gc): Remove.
        (strstr): Remove.