Add missing x_device rules for XI2 functions, from Eamon Walsh.
    
    > Whats the difference between add/remove and create/destroy?
    >
    > The devices are in a kind of hierarchy.  You can now create one or more
    > "master devices" (mouse cursor and keyboard focus).  The physical input
    > devices are "slave devices" that attach to master devices.
    >
    > Add/remove controls the ability to add/remove slave devices from a
    > master device.  Create/destroy controls the ability to create new master
    > devices.