Small cleanup by using std::shared_ptr and getting rid of
ciface.Devices() which just returned the m_devices (which defeats the
point of making m_devices protected).
Incidentally, this should make the code safer when we have
different threads accessing devices in the future (for hotplug?).
A lot of code use Device references directly so there is
no easy way to remove FindDevice() and make those unique_ptrs.
My keyboard layout does not have Alt_R but ISO_Level3_Shift. As a
consequence any control expression containing Alt_R fails to evaluate
completely and is unusable. This modification replace the missing term
of the expression by a dummy expression which always evaluate to
0. This way, the keybinding can work even if some keys are not
available.