What's new:
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What changed:
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Bug Fixes
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- Fix the problem that `ps' or `pstree' may show up in their own output twice.
  Addresses: Report on IRC

- Honor setting uc_sigmask in a sigaction signal handler.
  Addresses: https://cygwin.com/ml/cygwin/2019-04/msg00016.html

- Fix signal handling if setcontext is called from a signal handler.
  Addresses: Self-tested.