More Doxygen updates for multiple architecture support.

LUFA/Common/Architectures.h

LUFA/Common/Attributes.h

LUFA/Common/BoardTypes.h

LUFA/Common/Common.h

LUFA/Drivers/Board/Buttons.h

LUFA/Drivers/Board/Dataflash.h

LUFA/Drivers/Board/Joystick.h

LUFA/Drivers/Board/LEDs.h

LUFA/Drivers/Board/Temperature.h

LUFA/Drivers/Misc/RingBuffer.h

LUFA/Drivers/Misc/TerminalCodes.h

LUFA/Drivers/Peripheral/ADC.h

LUFA/Drivers/Peripheral/SPI.h

LUFA/Drivers/Peripheral/Serial.h

LUFA/Drivers/Peripheral/TWI.h

LUFA/Drivers/USB/Class/Common/HIDParser.h

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

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

LUFA/Drivers/USB/Core/Device.h

LUFA/Drivers/USB/Core/Endpoint.h