[QML frontend] Using pixelDelta instead of angleDelta for scrolling events 

angleDelta is pretty unusable, at least on Mac OS X : when I scroll with my mouse a little bit, the code code view scrolls too fast
using pixelDelta makes the scrolling far more usable
Did you try `angleDelta` with the smaller multiplier too? I suspect that will be what's slowed the scroll speed for you.

On my Linux machine, the reduction in the multiplier has made the scrolling much too slow.