Update AudioTrack comments to match AudioRecord

            void*       raw;

            short*      i16;      // signed 16-bit

            int8_t*     i8;       // unsigned 8-bit, offset by 0x80

        };                        // input: unused, output: pointer to buffer

        };                        // input to obtainBuffer(): unused, output: pointer to buffer

    };

    /* As a convenience, if a callback is supplied, a handler thread