Rotate with two-finger trackpad swipes should follow same principle as
for panning. This is first commit - for clarity.
Remaining issue is that for each system preset (in your OS) blender should
work as you expect too... pan, rotate and zoom gestures might need
each an own direction preset. Might be also messy, but then things can at
least work for everyone. Thinking it over and testing more now.
82d6b17662