Expose USBDevice object in USBAPI header

Author: facchinm

Diff for: cores/arduino/USB/USBAPI.h

@@ -90,6 +90,7 @@ class USBDeviceClass {
 private:
 	bool initialized;
 };
+extern USBDeviceClass USBDevice;
 
 //================================================================================
 //	Serial over CDC (Serial1 is the physical port)