Consider showing platform-specific signal value in exception cases

This issue was created automatically from an original Mantis Issue. Further discussion may take place here.

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We occasionally see tests terminate via signals, and CTest simply reports e.g.

4/123 Test 0000030: server_api_describe ..........................................................***Exception: Other

It would help with debugging if instead of simply "Exception: Other", it also included the platform-specific signal value, e.g. "Exception: Other (9)" or "Exception: Other (SIGKILL)".