Strace-process-tree

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* Recommend strace options in --help message.
* Add a file containing example output.

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* Fix strace files that have two spaces between pid and event.

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* Add output example.
* Fix incorrect assumption that strace files always had two spaces between the
pid and the event.

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* Add Unicode line art.

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* First public release as a GitHub Gist at
https://gist.github.com/mgedmin/4953427