Updated alvaBC6 driver:

Updated alvaBC6 driver:
	* Use a callback instead of a polling timer to retrieve key presses. This requires an updated alvaw32.dll (version 3.0.4.1 or later).
	* Rewrote key handling code to use InputGestures. It is now possible to map any of the display's keys.
	* Map braille navigation scripts to appropriate gestures.
Note that display keys that previously emulated system keyboard keys haven't yet been mapped, nor have display keys which changed the braille cursor.