libc/locale: support iconv_open,iconv,iconv_close

Refs to:https://github.com/bminor/musl

Signed-off-by: dongjiuzhu1 <dongjiuzhu1@xiaomi.com>

LICENSE

@@ -6615,6 +6615,38 @@ LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 SUCH DAMAGE.
 
+libs/libc/locale/big5.h
+libs/libc/locale/codepages.h
+libs/libc/locale/gb18030.h
+libs/libc/locale/hkscs.h
+libs/libc/locale/jis0208.h
+libs/libc/locale/ksc.h
+libs/libc/locale/legacychars.h
+libs/libc/locale/revjis.h
+libs/libc/locale/lib_iconv.c
+===================
+
+Copyright © 2005-2020 Rich Felker, et al.
+
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of this software and associated documentation files (the
+"Software"), to deal in the Software without restriction, including
+without limitation the rights to use, copy, modify, merge, publish,
+distribute, sublicense, and/or sell copies of the Software, and to
+permit persons to whom the Software is furnished to do so, subject to
+the following conditions:
+
+The above copyright notice and this permission notice shall be
+included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
 drivers/wireless/bluetooth/bt_uart.c
 drivers/wireless/bluetooth/bt_uart.h
 wireless/bluetooth