Merge pull request #121 from NicoHood/internalserial

Allow user override of the USE_INTERNAL_SERIAL serial number string index (thanks to Nicohood).

LUFA/Drivers/USB/Core/AVR8/Device_AVR8.h

@@ -113,7 +113,9 @@
 				 *  On unsupported devices, this will evaluate to \ref NO_DESCRIPTOR and so will force the host to create a pseudo-serial
 				 *  number for the device.
 				 */
+				#ifndef USE_INTERNAL_SERIAL
 				#define USE_INTERNAL_SERIAL            0xDC
+				#endif
 
 				/** Length of the device's unique internal serial number, in bits, if present on the selected microcontroller
 				 *  model.

LUFA/Drivers/USB/Core/UC3/Device_UC3.h

@@ -102,7 +102,9 @@
 				 *  On unsupported devices, this will evaluate to \ref NO_DESCRIPTOR and so will force the host to create a pseudo-serial
 				 *  number for the device.
 				 */
+				#ifndef USE_INTERNAL_SERIAL
 				#define USE_INTERNAL_SERIAL             0xDC
+				#endif
 
 				/** Length of the device's unique internal serial number, in bits, if present on the selected microcontroller
 				 *  model.

LUFA/Drivers/USB/Core/XMEGA/Device_XMEGA.h

@@ -110,7 +110,9 @@
 				 *  On unsupported devices, this will evaluate to \ref NO_DESCRIPTOR and so will force the host to create a pseudo-serial
 				 *  number for the device.
 				 */
+				#ifndef USE_INTERNAL_SERIAL
 				#define USE_INTERNAL_SERIAL            0xDC
+				#endif
 
 				/** Length of the device's unique internal serial number, in bits, if present on the selected microcontroller
 				 *  model.