Use different USB warnings for separate board types

This also throws an #error if using an unknown board where USB_XINPUT (the USB API) isn't defined. The library would still print debug info, mind you, but this way it's very explicit to the novice: "THIS WON'T WORK DON'T EVEN TRY".

Author: dmadison

src/XInput.cpp

@@ -26,20 +26,33 @@
 
 #include "XInput.h"
 
-#ifndef USB_XINPUT
-#warning "USB type is not set to XInput in boards menu! Using debug print - board will not behave as an XInput device"
-#endif
-
-#if defined(TEENSYDUINO)
+ // AVR Board with USB support
+#if defined(USBCON)
+	#ifndef USB_XINPUT
+		#warning "Non-XInput version selected in boards menu! Using debug print - board will not behave as an XInput device"
+	#endif
+
+// Teensy 3 Boards
+#elif defined(TEENSYDUINO)
 	// Teensy 3.1-3.2:  __MK20DX256__
 	// Teensy LC:       __MKL26Z64__
 	// Teensy 3.5:      __MK64FX512__
 	// Teensy 3.6:      __MK66FX1M0__
-#if  !defined(__MK20DX256__) && !defined(__MKL26Z64__) && \
-	 !defined(__MK64FX512__) && !defined(__MK66FX1M0__)
-	#warning "Not a supported board! Must use Teensy 3.1/3.2, LC, 3.5, or 3.6"
-#endif /* if supported Teensy board */
-#endif /* if defined(TEENSYDUINO) */
+	#if  !defined(__MK20DX256__) && !defined(__MKL26Z64__) && \
+		 !defined(__MK64FX512__) && !defined(__MK66FX1M0__)
+		#warning "Not a supported board! Must use Teensy 3.1/3.2, LC, 3.5, or 3.6"
+	#elif !defined(USB_XINPUT)
+		#warning "USB type is not set to XInput in boards menu! Using debug print - board will not behave as an XInput device"
+	#endif /* if supported Teensy board */
+
+// Everything else
+#else
+	#ifdef USB_XINPUT
+		#warning "Unknown board. XInput may not work properly."
+	#else
+		#error "This board does not support XInput!"
+	#endif
+#endif /* if supported board */
 
 // --------------------------------------------------------
 // XInput Button Maps                                     |