message: Make compatibility with Teensyduino 1.47
diff: #ifndef _AudioStream_F32_h
  #define _AudioStream_F32_h
  -#include <arm_math.h> //ARM DSP extensions. for speed!
  //include <Audio.h> //Teensy Audio Library
  -#include <AudioStream.h> //needed for AUDIO_BLOCK_SAMPLES
  +#include "arm_math.h" //simply to define float32_t
  +#include <core_pins.h> //for F_CPU_ACTUAL ??
  +#include <AudioStream.h>
  #include "AudioSettings_F32.h"
  +#if defined(__IMXRT1062__) //for Teensy 4...this shouldn't be necessary
  +extern volatile uint32_t F_CPU_ACTUAL;
  +#endif
  // /////////////// class prototypes
  class AudioStream_F32;
  