codecvt.h: Implement codecvt<wchar_t, char, mbstate_t>.

2000-08-21  Benjamin Kosnik  <bkoz@purist.soma.redhat.com>

	* bits/codecvt.h: Implement codecvt<wchar_t, char, mbstate_t>. Fix
	up __enc_traits template so as to be marginally useful.
	* src/codecvt.cc: And here.
	* bits/char_traits: Tweak.
	* bits/locale_facets.h: Tweak.
	* bits/locale_facets.tcc: Tweak.
	* bits/localefwd.h: Tweak.
	* src/locale-inst.cc: Add use_facet/has_facet instantiations here.
	* testsuite/22_locale/codecvt_wchar_t_cc.cc: New file.
	* testsuite/22_locale/codecvt_char_char.cc: New file.
	* testsuite/22_locale/codecvt_unicode_char.cc: New file.

From-SVN: r35871