Update gettext-runtime files from gnulib.

Update gettext-runtime files from gnulib.

* Makefile.am (distcheck-hook): Check also flexmember.m4, flexmember.h.
* gettext-runtime/intl/Makefile.in (SOURCES): Add flexmember.h.
* gettext-runtime/intl/flexmember.h: New file, from gnulib.
* gettext-runtime/intl/localcharset.c:
  * localcharset.c (relocate2): Define fallback.
  (get_charset_aliases): Invoke relocate2 instead of relocate. Free the
  allocated memory.
  * localcharset.c (WINDOWS_NATIVE): Don't define on Cygwin.
  * localcharset.c (locale_charset) [WINDOWS_NATIVE]: Don't use the
  return value from setlocale if it would lead to a buffer overrun.
* gettext-runtime/intl/localename.c:
  * localename.c [__CYGWIN__]: Include <langinfo.h>, since this is
  where NL_LOCALE_NAME is defined.
  * localename.c (WINDOWS_NATIVE): Don't define on Cygwin.
  * localename.c (gl_locale_name_thread_unsafe): Add clause for
  Cygwin.
  * localename.c (struct hash_node): Use FLEXIBLE_ARRAY_MEMBER.
* gettext-runtime/intl/lock.c:
  * lock.c: On glibc systems without
  PTHREAD_RWLOCK_WRITER_NONRECURSIVE_INITIALIZER_NP, use the fallback
  implementation of rwlocks.
  * lock.c [USE_POSIX_THREADS]
  (glthread_rwlock_init_for_glibc): New function.
  [USE_POSIX_THREADS] (glthread_rwlock_rdlock_multithreaded): Update
  comment.
  [USE_PTH_THREADS]: New implementation of rwlocks.
  [USE_WINDOWS_THREADS] (glthread_rwlock_rdlock_func): Prefer writers over
  readers.
* gettext-runtime/intl/lock.h:
  * lock.h (pthread_rwlockattr_setkind_np): Don't declare
  weak on non-glibc platforms.
  * lock.h: On glibc systems without
  PTHREAD_RWLOCK_WRITER_NONRECURSIVE_INITIALIZER_NP, use the fallback
  implementation of rwlocks.
  * lock.h [USE_POSIX_THREADS_WEAK]: Declare also
  pthread_rwlockattr_init, pthread_rwlockattr_setkind_np,
  pthread_rwlockattr_destroy weak.
  * lock.h [USE_POSIX_THREADS]: Test
  HAVE_PTHREAD_RWLOCK_RDLOCK_PREFER_WRITER. Use a different implementation
  of rwlock initialization on glibc systems without
  HAVE_PTHREAD_RWLOCK_RDLOCK_PREFER_WRITER. Use a different implementation
  of rwlocks altogether on non-glibc systems without
  HAVE_PTHREAD_RWLOCK_RDLOCK_PREFER_WRITER.
  [USE_PTH_THREADS]: Use a different implementation of rwlocks altogether.
* gettext-runtime/intl/relocatable.c:
  * relocatable.c (relocate2): New function.
  * relocatable.c (relocate): Assume pathname is non-NULL. Use
  ISSLASH macro consistently. Avoid dangerous string concatenation idiom.
* gettext-runtime/intl/relocatable.h:
  * relocatable.h (relocate2): New declaration/macro.
* gettext-runtime/intl/vasnprintf.c, gettext-runtime/libasprintf/vasnprintf.c:
  * vasnprintf.c (FALLTHROUGH): New macro.
  Use it whenever one switch case falls through into the next.
  * vasnprintf.c (USE_MSVC__SNPRINTF): New macro.
  Everywhere, use !HAVE_SNPRINTF_RETVAL_C99 || USE_MSVC__SNPRINTF instead
  of !HAVE_SNPRINTF_RETVAL_C99.
  * vasnprintf.c (VASNPRINTF): Move comment down past two cpp
  directives, so that it takes effect once again.  This is clearly
  not a proper change, and I will revert it once this bug is fixed:
  https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77817
  * vasnprintf.c (IF_LINT): Treat GCC_LINT like lint.
* gettext-runtime/intl/verify.h:
  * verify.h (verify) [!__GNUC__]:
  Use shorter albeit meaningless string to bypass silly compiler limits.
  * verify.h (assume): Treat GCC_LINT like lint.
* gettext-runtime/intl/xsize.h: Update.
* gettext-runtime/m4/Makefile.am (EXTRA_DIST): Add flexmember.m4.
* gettext-runtime/m4/extern-inline.m4: Update.
* gettext-runtime/m4/fcntl-o.m4: Update.
* gettext-runtime/m4/flexmember.m4: New file, from gnulib.
* gettext-runtime/m4/glibc2.m4: Update.
* gettext-runtime/m4/glibc21.m4: Update.
* gettext-runtime/m4/intdiv0.m4: Update.
* gettext-runtime/m4/intl.m4 (AM_INTL_SUBDIR): Require AC_C_FLEXIBLE_ARRAY_MEMBER.
* gettext-runtime/m4/intmax.m4: Update.
* gettext-runtime/m4/inttypes-pri.m4: Update.
* gettext-runtime/m4/inttypes_h.m4: Update.
* gettext-runtime/m4/lock.m4 (gl_LOCK): Invoke gl_PTHREAD_RWLOCK_RDLOCK_PREFER_WRITER.
* gettext-runtime/m4/longlong.m4: Update.
* gettext-runtime/m4/printf-posix.m4: Update.
* gettext-runtime/m4/progtest.m4: Update.
* gettext-runtime/m4/size_max.m4: Update.
* gettext-runtime/m4/stdint_h.m4: Update.
* gettext-runtime/m4/threadlib.m4 (gl_THREADLIB_BODY): Don't set
PTHREAD_IN_USE_DETECTION_HARD if configuring on Solaris 10 or newer.
Reported by Peter Felecan at <https://savannah.gnu.org/bugs/?32087>.
* gettext-runtime/m4/uintmax_t.m4: Update.
* gettext-runtime/m4/visibility.m4: Update.
* gettext-runtime/m4/wchar_t.m4: Update.
* gettext-runtime/m4/xsize.m4: Update.
* gettext-runtime/tests/test-lock.c:
  * test-lock.c: On Mac OS X, use named semaphores, not unnamed
  semaphores.
  (USE_NAMED_SEMAPHORE, USE_UNNAMED_SEMAPHORE): New macros.
  (atomic_int_semaphore): New macro.
  * test-lock.c (USE_SEMAPHORE): Don't set if <semaphore.h> does not
  exist.
  * test-lock.c (USE_SEMAPHORE): New constant.
  (struct atomic_int, init_atomic_int, get_atomic_int_value,
  set_atomic_int_value) [USE_SEMAPHORE]: Define using a POSIX semaphore.
  Suggested by Torvald Riegel <triegel@redhat.com>.