MFC: r286490,r286491,r287125

Per rfc3629 value greater than 0x10ffff should be rejected (r286490,r286491)

Make UTF-8 parsing and generation more strict. (r287125 by ed)

• in mbrtowc() we need to disallow codepoints above 0x10ffff.
• In wcrtomb() we need to disallow codepoints between 0xd800 and 0xdfff.