Add XMEGA TWI peripheral driver to the Atmel Studio extension XML.

LUFA/StudioIntegration/lufa_drivers_peripheral.xml

@@ -144,7 +144,10 @@
 
 				<require idref="lufa.common"/>
 
-				<info type="gui-flag" value="hidden"/>
+				<build type="c-source" value="Drivers/Peripheral/XMEGA/TWI_XMEGA.c"/>
+				<build type="header-file" value="Drivers/Peripheral/XMEGA/TWI_XMEGA.h"/>
+				<build type="include-path" value=".."/>
+				<build type="header-file" subtype="api" value="Drivers/Peripheral/TWI.h"/>
 			</module>
 
 			<module type="driver" id="lufa.drivers.peripheral.twi#uc3" caption="LUFA TWI Master Driver - UC3">