MIDI: Add raw USB packet interface

Add methods to send and retrieve a full 4-byte USB MIDI packet:
  bool send(const MIDIPacket* packet);
  bool receive(MIDIPacket* packet);

Author: kaysievers

src/Adafruit_USBD_MIDI.cpp

@@ -114,4 +114,14 @@ void Adafruit_USBD_MIDI::flush(void) {
   // MIDI Library doen't use flush
 }
 
+bool Adafruit_USBD_MIDI::send(const uint8_t packet[4])
+{
+  return tud_midi_send(packet);
+}
+
+bool Adafruit_USBD_MIDI::receive(uint8_t packet[4])
+{
+  return tud_midi_receive(packet);
+}
+
 #endif

src/Adafruit_USBD_MIDI.h

@@ -47,6 +47,10 @@ class Adafruit_USBD_MIDI : public Stream, Adafruit_USBD_Interface {
   virtual int peek(void);
   virtual void flush(void);
 
+  // Raw MIDI USB packet interface.
+  bool send(const uint8_t packet[4]);
+  bool receive(uint8_t packet[4]);
+
   // from Adafruit_USBD_Interface
   virtual uint16_t getDescriptor(uint8_t itfnum, uint8_t *buf,
                                  uint16_t bufsize);