Switch board check errors to warnings

Allows the library to compile if the user is building for an unknown setup and has defined their own USB functions.

Author: dmadison

src/XInput.cpp

@@ -36,11 +36,11 @@
 	 defined(__MK64FX512__) || defined(__MK66FX1M0__))
 
 	#ifndef USB_XINPUT
-	#error "USB type is not set to XInput in boards menu!"
+	#warning "USB type is not set to XInput in boards menu! Board will not behave as an XInput device"
 	#endif
 
 #else
-#error "Not a supported board! Must use Teensy 3.1/3.2, LC, 3.5, or 3.6"
+#warning "Not a supported board! Must use Teensy 3.1/3.2, LC, 3.5, or 3.6"
 #endif
 
 // --------------------------------------------------------