intl: Export libintl_{new,dup,free}locale from libintl.so on OpenBSD.

intl: Export libintl_{new,dup,free}locale from libintl.so on OpenBSD.

Reported by Christian Weisgerber <naddy@mips.inka.de>.

* gnulib-local/lib/getlocalename_l-unsafe.c.diff: New file.
* gnulib-local/Makefile.am (EXTRA_DIST): Add it.
* gettext-runtime/intl/configure.ac (rpl_newlocale, rpl_duplocale,
rpl_freelocale): Redirect to symbols prefixed with 'libintl_', not '_libintl_'.
* gettext-runtime/intl/Makefile.am (BUILT_SOURCES): Add libgnuintl.h.