Crash with CoreUI

[TehFlaminTaco]

Scrolling the mousewheel on a CoreUI NativeWindow causes a System.OverflowExecption, prior to executing the event.

Occurs when running Core 3.0 compiling for win-x64

[TehFlaminTaco]

When attempting to hack-patch this, I discovered that the MouseWheelEvent has room for WheelTicks, but never actually implements it.

[luca-piccioni]

Good catch. The CoreUI sub-project was an experiment about windows with .NET Core, indeed some code may be never executed.

Feel free to PR a patch, I'll integrate it happily.