In order to give NewInputDeviceRequest more information, a new
InputAttributes type is introduced. Currently, this collects the product
and vendor name, device path, and sets booleans for attributes such as
having keys and/or a pointer. Only the HAL backend fills in the
attributes, though.

Signed-off-by: Dan Nicholson <dbn.lists@gmail.com>
Reviewed-by: Peter Hutterer <peter.hutterer at who-t.net>