Android/NEWT MouseEvent: Fix Detection/Processing of 2-Finger-Scroll Gesture - Part 2

Multiple tests on different devices disclosed that:
  - 1 of 2 pointers get disconnected every now and then ..
    -> Shall tolerate this case

  - dist-delta within gesture may shrink below doubleTouchSlope
    -> Remove constraint after gesture detection

- Always validate pointer-id

GearsES2
  - Works quite stable on several devices now
  - Moved soft-keyboad show to 4-pointer pressed >= 0.7f pressure