Rename AVRU4U6U9 peripheral driver directory to AVR8.

LUFA/Drivers/Peripheral/ADC.h

@@ -62,7 +62,7 @@
 		     defined(__AVR_AT90USB1287__) || defined(__AVR_AT90USB647__) || \
 			 defined(__AVR_ATmega16U4__)  || defined(__AVR_ATmega32U4__) || \
 			 defined(__AVR_ATmega32U6__))
-			#include "AVRU4U6U7/ADC.h"
+			#include "AVR8/ADC.h"
 		#else
 			#error "ADC is not available for the currently selected AVR model."
 		#endif

LUFA/Drivers/Peripheral/SPI.h

@@ -62,7 +62,7 @@
 		#if defined(__AVR32__)
 			#include "AVR32/SPI.h"
 		#else
-			#include "AVRU4U6U7/SPI.h"		
+			#include "AVR8/SPI.h"		
 		#endif
 		
 #endif

LUFA/Drivers/Peripheral/Serial.h

@@ -63,7 +63,7 @@
 		#if defined(__AVR32__)
 			#include "AVR32/Serial.h"
 		#else
-			#include "AVRU4U6U7/Serial.h"		
+			#include "AVR8/Serial.h"		
 		#endif
 		
 		#include "../../Common/Common.h"

LUFA/Drivers/Peripheral/TWI.h

@@ -61,7 +61,7 @@
 		     defined(__AVR_AT90USB1287__) || defined(__AVR_AT90USB647__) || \
 			 defined(__AVR_ATmega16U4__)  || defined(__AVR_ATmega32U4__) || \
 			 defined(__AVR_ATmega32U6__))
-			#include "AVRU4U6U7/TWI.h"
+			#include "AVR8/TWI.h"
 		#else
 			#error "TWI is not available for the currently selected AVR model."
 		#endif