Add more include protection macros to give the user warnings when they try to manually include private driver header files, instead of the public driver headers.

LUFA/Drivers/USB/HighLevel/USBMode.h

@@ -43,6 +43,11 @@
 #ifndef __USBMODE_H__
 #define __USBMODE_H__
 
+	/* Preprocessor Checks: */
+		#if !defined(__INCLUDE_FROM_USB_DRIVER)
+			#error Do not include this file directly. Include LUFA/Drivers/USB.h instead.
+		#endif
+		
 	/* Public Interface - May be used in end-application: */
 	#if defined(__DOXYGEN__)
 		/** Indicates that the target AVR microcontroller belongs to the Series 2 USB controller