#13 Conditionally suppress mouse-movement propagation

[Max Barraclough]

(For FOX 1.7.80.)

In most GUI toolkits, if a modal window is shown, then if the user should mouse-over widgets of background windows (i.e. windows other than the modal one) then those widgets will not visually 'pop' as they usually would. (FXMenuTitle widgets are a good example.) Currently, FOX does not behave this way, and those widgets 'pop' as usual.
I had a go at bringing FOX into line with other toolkits in this regard.

Testing

I've tested my changes on Windows and on Kubuntu by:

1. Launch Adie
2. Hover mouse of FXMenuTitle widgets of the main Adie window, ensuring normal response (they should visually 'pop' when hovered over)
3. Bring up the About dialog (Help > About Adie...)
4. Hover the mouse over the FXMenuTitle widgets of the main Adie window

Expected outcome of Stage 4, prior to changes: the FXMenuTitle widgets 'pop' when hovered over.

Expected outcome of Stage 4, after applying changes: the FXMenuTitle widgets will not respond when hovered over.