Test with -Wextra, fix library warnings due to unused function parameters.

Demos/Host/ClassDriver/MassStorageHost/makefile

LUFA/Drivers/Peripheral/SerialStream.c

LUFA/Drivers/USB/Class/Device/Audio.c

LUFA/Drivers/USB/Class/Device/Audio.h

LUFA/Drivers/USB/Class/Device/MIDI.c

LUFA/Drivers/USB/Class/Device/RNDIS.c

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

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

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

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

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

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

LUFA/ManPages/ChangeLog.txt