Update after Turkey changed its name.
* gettext-tools/doc/ISO_3166: Update country name.
* gettext-tools/doc/iso-3166.texi: Likewise.
* gettext-tools/doc/ISO_639-2: Update comments.
* gettext-runtime/intl/setlocale.c: Likewise.
* gettext-tools/src/msginit.c: Likewise.
