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
26d7d995db