macOS: trackpad support

It seems UTM emulates some kind of mouse, and not trackpad, which means:
- vertical scrolling only
- weird scrolling which appears to simulate a mouse wheel behavior (ie.: it starts scrolling after a huge finger swipe, and it skips lines, not pixels, so it's not precise at all, unlike a real trackpad on Mac (or even Windows)
- no gestures support (pinch to zoom, etc...)

I which there was a way to make Windows use the mac's trackpad when available, and not emulate a simple mouse instead.