Input: aiptek - rework the function key code

Function keys (also called macro keys) code corrected. Using a
lastMacro variable to keep track of key currently pressed. This
ensures proper resetting when dragging the pen in the drawing
area or to another key. Also suppress sending pressure reports
when over the macro key area.

Signed-off-by: Rene van Paassen <rene.vanpaassen@gmail.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>