Made USP-API included flexible

Author: NicoHood

Diff for: hardware/arduino/avr/cores/arduino/USBAPI.h

@@ -67,6 +67,7 @@ class USBDevice_
 	bool wakeupHost(); // returns false, when wakeup cannot be processed
 };
 extern USBDevice_ USBDevice;
+void setupUSB();
 
 //================================================================================
 //================================================================================

Diff for: hardware/arduino/avr/cores/arduino/USBCore.cpp

@@ -828,4 +828,8 @@ bool USBDevice_::wakeupHost()
 	return false;
 }
 
+void setupUSB() {
+	USBDevice.attach();
+}
+
 #endif /* if defined(USBCON) */

Diff for: hardware/arduino/avr/cores/arduino/main.cpp

@@ -28,7 +28,11 @@ void initVariant() __attribute__((weak));
 void initVariant() { }
 
 void setupUSB() __attribute__((weak));
-void setupUSB() { }
+void setupUSB() {
+#if defined(USBCON) && (MAGIC_KEY_POS != (RAMEND-1))
+	USBDevice.attach();
+#endif
+}
 
 int main(void)
 {
@@ -37,9 +41,9 @@ int main(void)
 	initVariant();
 
 #if defined(USBCON)
-	USBDevice.attach();
+	setupUSB();
 #endif
-	
+
 	setup();
 
 	for (;;) {