* ctype.cc (_CTYPE_DATA_0_127): Add _B class to TAB character.

	* ctype.cc (_CTYPE_DATA_0_127): Add _B class to TAB character.
	(__ctype_default): New character class array for default ASCII
	character set.
	(__ctype_iso): New array of character class array for ISO charsets.
	(__ctype_cp): Ditto for singlebyte Windows codepages.
	(tolower): Implement as distinct function to support any singlebyte
	charset.
	(toupper): Ditto.
	(__set_ctype): New function to copy singlebyte character classes
	corresponding to current charset to ctype_b array.
	Align copyright text to upstream.
	* dcrt0.cc (dll_crt0_1): Reset current locale to "C" per POSIX.
	* environ.cc (set_file_api_mode): Remove.
	(codepage_init): Remove.
	(parse_thing): Remove "codepage" setting.
	(environ_init): Set locale according to environment settings, or
	to current codepage, before converting environment to multibyte.
	* fhandler.h (fhandler_console::write_replacement_char): Drop argument.
	* fhandler_console.cc (dev_console::str_to_con): Call sys_cp_mbstowcs
	rather than MultiByteToWideChar.
	(fhandler_console::write_replacement_char): Always print a funny
	half filled square if a character isn't in the current charset.
	(fhandler_console::write_normal): Convert to using __mbtowc
	rather than next_char.
	* fork.cc (frok::child): Drop call to set_file_api_mode.
	* globals.cc (enum codepage_type) Remove.
	(current_codepage): Remove.
	* miscfuncs.cc (cygwin_wcslwr): Unused, dangerous.  Remove.
	(cygwin_wcsupr): Ditto.
	(is_cp_multibyte): Remove.
	(next_char): Remove.
	* miscfuncs.h (is_cp_multibyte): Drop declaration.
	(next_char): Ditto.
	* strfuncs.cc (get_cp): Remove.
	(__db_wctomb): New function to implement _wctomb_r functionality for
	doublebyte charsets using WideCharToMultiByte.
	(__sjis_wctomb): New function to replace unusable newlib function.
	(__jis_wctomb): Ditto.
	(__eucjp_wctomb): Ditto.
	(__gbk_wctomb): New function.
	(__kr_wctomb): Ditto.
	(__big5_wctomb): Ditto.
	(__db_mbtowc): New function to implement _mbtowc_r functionality for
	doublebyte charsets using MultiByteToWideChar.
	(__sjis_mbtowc): New function to replace unusable newlib function.
	(__jis_mbtowc): Ditto.
	(__eucjp_mbtowc): Ditto.
	(__gbk_mbtowc): New function.
	(__kr_mbtowc): New function
	(__big5_mbtowc): New function
	(__set_charset_from_codepage): New function.
	(sys_wcstombs): Reimplement, basically using same wide char to multibyte
	conversion as newlib's application level functions.  Plus extras.
	Add lengthy comment to explain.  Change return type to size_t.
	(sys_wcstombs_alloc): Just use sys_wcstombs.  Change return type to
	size_t.
	(sys_cp_mbstowcs): Replace sys_mbstowcs, take additional codepage
	argument.  Explain why.  Change return type to size_t.
	(sys_mbstowcs_alloc): Just use sys_mbstowcs.  Change return type to
	size_t.
	* wchar.h: Declare internal functions implemented in strfuncs.cc.
	(wcscasecmp): Remove.
	(wcsncasecmp): Remove.
	(wcslwr): Remove.
	(wcsupr): Remove.
	* winsup.h (codepage_init): Remove declaration.
	(get_cp): Ditto.
	(sys_wcstombs): Align declaration to new implementation.
	(sys_wcstombs_alloc): Ditto.
	(sys_cp_mbstowcs): Add declaration.
	(sys_mbstowcs): Define as inline function.
	(sys_mbstowcs_alloc): Align declaration to new implementation.
	(set_file_api_mode): Remove declaration.
	* include/ctype.h (isblank): Redefine to use _B character class.
	(toupper): Remove ASCII-only definition.
	(tolower): Ditto.