Blender Git Loki

Fix: Property editor icon jittering in some cases

In the tools tab, the tool icon would be offset when it intersected
the bottom of the editor. With some screen resolutions, the icons on
the left side of the editor would also move when intersecting the
bottom of the editor. This happened because of the truncation in
the implicit conversion from float to int. Instead, use explicit
conversion functions.

Differential Revision: https://developer.blender.org/D11097