Touchpad-based spinning is too fast

[billdami]

When using a touchpad (tested from a Macbook Pro Retina, late 2013) to interact with the spin box, the spin speed is way too fast.

This is because the touchpad fires mousewheel events much more rapidly than an actual mouse scroll wheel, and each mousewheel event results in a spin/value change.

Need a way to normalize the event's delta value, and only invoke a spin/value change if it passes a certain threshold, but while still maintaining the same behavior for actual mouse wheel scrolling.