Add host mode USB Class driver stubs, add beginnings of a CDC host class driver.

Split out common defines/types from class drivers into a seperate common class driver directory.

Make central USB Class driver dispatch headers, used for both device and host modes.

LUFA/Drivers/USB/Class/Host/HIDParser.c

@@ -29,6 +29,7 @@
 */
 
 #include "HIDParser.h"
+#if defined(CAN_BE_HOST)
 
 uint8_t USB_ProcessHIDReport(const uint8_t* ReportData, uint16_t ReportSize, HID_ReportInfo_t* const ParserData)
 {
@@ -324,3 +325,5 @@ void USB_SetHIDReportItemInfo(uint8_t* ReportData, const HID_ReportItem_t* Repor
 		BitMask <<= 1;
 	}
 }
+
+#endif