* include/stdint.h (INT8_C): Also define for __cplusplus >= 201103L.
        If __INT8_C is defined, use GNU C preprocessor builtin-macro
        for the definition.
        (INT16_C INT32_C, INT64_C, UINT8_C, UINT16_C, UINT32_C): Likewise.
        (UINT64_C, INTMAX_C, UINTMAX_C): Likewise.