Blender Git Loki

WM: de-duplicate cursor motion checks for selection picking

Replace local static mouse coordinate storage with a single function.
also resolve inconsistencies.

- Edit-mesh selection used equality check (ignoring `U.move_threshold`).
- Motion to clear tooltips checked the value without scaling by the DPI.

Also prevent the unlikely case of the previous motion check matching
a different area by resetting the value when the active region changes.