Don't import cysignals.alarm on Windows

[tobiasdiez]

cysignals.alarm is not available on Windows, so we don't try to import it. Probably more work needs to be done to actually fix the methods that make use of these methods on Windows; but that's left for further PRs.

Also remove a cysignals import from an all_xyz.py file that was duplicated in the main all.py file.

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