http://www.cppblog.com/Error/archive/2014/09/25/208413.html
// utf-8
char u8_array[] = u8"破晓的博客";
std::string u8_str = u8"破晓的博客";
// utf-16
char16_t u16_c = u'中';
char16_t u16_array[] = u"破晓的博客";
std::u16string u16_str = u"破晓的博客";
// ucs4
char32_t u32_c = U'破';
char32_t u32_array[] = U"破晓的博客";
std::u32string u32_str = U"破晓的博客";
std::wstring_convert<std::codecvt_utf8<char32_t>, char32_t> utf8_ucs4_cvt;
std::u32string ucs4_cvt_str = utf8_ucs4_cvt.from_bytes(u8_source_str);