Blender Git Loki

Fix Windows mouse wheel scroll speed

In Windows, event dispatching code is throwing out the wheel scroll count value.
Despite of how many fast you move the wheel, it only make one-notch scroll event.

This patch convert wheel event to multiple 1-notch wheel events.

This also correct the handling of smooth scroll mouse wheel (which can report smaller than 1-notch wheel movement) by accumulating the small wheel delta values.

Reviewers: djnz, shadowrom, elubie, #platform:_windows, sergey, juicyfruit, brecht

Reviewed By: shadowrom, elubie, #platform:_windows, brecht

Subscribers: dingto, elubie, brachi, brecht

Differential Revision: https://developer.blender.org/D143