intl: Improve support for per-thread locales on Solaris 11.4.

intl: Improve support for per-thread locales on Solaris 11.4.

* gettext-runtime/intl/localename.c: Update from gnulib:
Handle HAVE_SOLARIS114_LOCALES through Solaris specific code.
* gettext-runtime/intl/localename-table.in.h: Update from gnulib's
localename-table.h.
* gettext-runtime/intl/localename-table.c: Update from gnulib.
* gettext-runtime/m4/intl-thread-locale.m4: Renamed from
gettext-runtime/m4/intlsolaris.m4.
(gt_INTL_THREAD_LOCALE_NAME): Renamed from gt_INTL_SOLARIS. Define
HAVE_SOLARIS114_LOCALES instead of HAVE_NAMELESS_LOCALES.
* gettext-runtime/m4/intl.m4: Update from gnulib:
(AM_INTL_SUBDIR): Require gt_INTL_THREAD_LOCALE_NAME. Test for 'uselocale'. Set
HAVE_NAMELESS_LOCALES.
(gt_INTL_SUBDIR_CORE): Don't invoke gt_INTL_SOLARIS. Don't set
HAVE_NAMELESS_LOCALES here.
* gettext-runtime/m4/Makefile.am (EXTRA_DIST): List intl-thread-locale.m4, not
intlsolaris.m4.
* gettext-tools/m4/Makefile.am (aclocal_DATA): List intl-thread-locale.m4, not
intlsolaris.m4.
* gettext-tools/misc/gettextize.in (m4filelist): List intl-thread-locale.m4, not
intlsolaris.m4.
* Makefile.am (distcheck-hook): Check intl-thread-locale.m4, not intlsolaris.m4.
* gettext-tools/doc/gettext.texi (aclocal): List intl-thread-locale.m4, not
intlsolaris.m4.
* PACKAGING: List intl-thread-locale.m4, not intlsolaris.m4.