* fhandler.h (class dev_console): Add members con_mbtowc, con_wctomb,
and con_charset.
(dev_console::str_to_con): Take mbtowc function pointer and charset
as additional parameters.
* fhandler_console.cc (fhandler_console::get_tty_stuff): Initialize
aforementioned new members. Explain why.
(dev_console::con_to_str): Remove useless comment. Call new
sys_cp_wcstombs function rather than sys_wcstombs.
(dev_console::str_to_con): Take mbtowc function pointer and charset
as additional parameters. Call sys_cp_mbstowcs accordingly.
(fhandler_console::write_normal): Only initialize f_mbtowc and charset
once. Accommodate changed str_to_con.
* strfuncs.cc (sys_cp_wcstombs): Renamed from sys_wcstombs. Take
wctomb function pointer and charset as parameters. Use throughout.
(sys_cp_mbstowcs): Take wctomb function pointer and charset as
parameters instead of codepage. Remove matching local variables and
their initialization.
* wchar.h (ENCODING_LEN): Define as in newlib.
(__mbtowc): Use mbtowc_p typedef for declaration.
(wctomb_f): New type.
(wctomb_p): New type.
(__wctomb): Declare.
(__utf8_wctomb): Use wctomb_f typedef for declaration.
(sys_cp_wcstombs): Move declaration from winsup.h here.
(sys_wcstombs): Ditto.
(sys_wcstombs_alloc): Ditto.
(sys_cp_mbstowcs): Ditto.
(sys_mbstowcs): Ditto.
(sys_mbstowcs_alloc): Ditto.
* winsup.h: Move declaration of sys_FOO functions to wchar.h. Include
wchar.h instead.