BZ #15969: search locale archive again after alias expansion

If a locale alias is defined in locale.alias but not in an archive,
and the referenced locale is only present in the archive, setlocale
will fail if given the alias name.  This is unintuitive.  This patch
fixes it, arranging for the locale archive to be searched again after
alias expansion.

for  ChangeLog

	[BZ #15969]
	* locale/findlocale.c (_nl_find_locale): Retry archive search
	after alias expansion.