Strace-process-tree

------------------

* New strace in Ubuntu 18.04 LTS formats its log files differently.
* Recognize fork().

------------------

* Use argparse, add help message.
* Better error reporting.
* Print just the command lines instead of execve() system call arguments
(pass -v/--verbose if you want to see full execve() calls like before).
* execve() is more important than clone().
* Distinguish threads from forks.
* This was the last version released as a Gist. Newer versions were available
from `my scripts repository
<https://github.com/mgedmin/scripts/blob/master/strace-process-tree>`__.

------------------

* Strip trailing whitespace in output.

------------------

* Handle strace -T output.
* Simplify clone() args in output.

------------------

* Support vfork() and fork().

------------------

* Support optional timestamps (strace -ttt).