* can be enabled by defining Makefile macro SERIAL_MOUSE_MICROSOFT_ENABLE or
   SERIAL_MOUSE_MOUSESYSTEMS_ENABLE.
 * Serial implementation can be chosen via SERIAL_MOUSE_USE_SOFT and
   SERIAL_MOUSE_USE_UART macros
 * UART configuration still has to be done in config.h: I added working clauses
   for both mouse protocols to ps2_usb's config.h

 * Both drivers use the interface defined in serial_mouse.h
 * They should work with any UART implementation (hardware/software UART)
 * The Microsoft driver is currently untested.
   The Mousesystems driver is confirmed to work.

- to support Adjustable keyboard(composite device?)

- without this fix wakeup often fails
- keyboard can wakeup once or twice but fails after that

- Command can force to enable NKRO even when boot mode
- After boot keyboard may be in boot mode due to BIOS' request

- NKRO is used only when keyboard_protocol = 1(report)

- change API of ps2_mouse; ps2_mouse_task()
- remove mouse_report from host.c

- <http://geekhack.org/index.php?topic=14290.msg1075201#msg1075201>

- Add delay between scans to prevent overlaod of ADB keyboard controllers
- <http://geekhack.org/index.php?topic=14290.msg1068919#msg1068919>

- Blocking occurs if built without option INTERRUPT_CONTROL_ENDPOINT

- Add print messages of USB intialize procesure.
- call out sei() in earlier stage. LUFA API doc of USB_Init() says:
interrupts must be enabled within 500ms ... to ensure that the host does
not time out whilst enumerating the device
- remove matrix_init() from suspend_wakeup_init(). It is not needed in
  fact and if matrix_init() takes long time to initialize it prevents
host emnumerating the device.