Blender Git Loki

Fix T40065: Pressing Esc in separate render result window does not focus main window.

The problem is that the render window keeps keybord input focus even after it has been
lowered. Windows maintains the Z-order of windows, so the present solution is to raise
the window that has been just below the render window.

Differential revision: https://developer.blender.org/D594
Reviewed by: campbellbarton