Fixes #3512. Ctrl+Z not suspending

[BDisp]

Fixes

• Fixes Ctrl+Z not suspending #3512

Proposed Changes/Todos

• Add #define UNIX_KEY_BINDINGS

Pull Request checklist:

• I've named my PR in the form of "Fixes #issue. Terse description."
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• My code follows the Terminal.Gui library design guidelines
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• I conducted basic QA to assure all features are working

[dodexahedron]

Rather than hot loops, you can just start a free-running timer at startup and an event handler when it ticks.

Should be like... half the code, if even that much.

[tig]

Good stuff. See my comments.