added Mouse.moveAbs() as a new feature for absolute mouse positioning as requested in issue #1417.
all parameters have the range of -32768 to 32767 and must be scaled to screen pixels
some examples:
  x=0, y=0 is the middle of the screen
  x=-32768, y=-32768 is the top left corner
  x=32767, y=-32768 is the top right corner
  x=32767, y=32767 is the bottom right corner
  x=-32768, y=32767 is the bottom left corner