`mkdir -p` and `os.makedirs()` functionality.  When true, ignore
  FileExistsErrors.  Patch by Berker Peksag.

(With minor cleanups, additional tests, doc tweaks, etc. by Barry)

Also:

* Remove some unused imports in test_pathlib.py reported by pyflakes.

Argument Clinic now generates a cast to that type for the comparison
to -1 in the generated code.  (This supresses a compilation warning.)

#18034: update FAQ to suggest importlib.import_module instead of __import__.  Patch by Wouter van Heyst.

Also, improve variable names and fix column numbers
in the generated output.

Use two-argument form of next() and use a return-statement instead of an explicit raise StopIteration

a, b in arg lists, and hanging indents for long arg lists.

Issue #13540: Update references to Action class to match syntax used for other classes in this file.