Effective rect of stacks on Windows 10

[Paul Dupuis]

Thank your Richard and Trevor.

When the 'effective rect' of a stack was introduced to provide the outer 
boundaries of a stack, along with the effective working screenRects(s), 
I rewrote all my complicated windows management code (and some of your 
clever tricks for Windows weirdness, Richard), to use simple elegant 
code that worked awesomely on all OSX versions and every Windows version 
until I tried it under Windows 10 and ...

Not one of my happier days :-(