This changeset fixes a number of compiler warnings in the Python Launcher
binary for OSX. It also cleans up whitespace usage in those sources.

Reformulated the textual change, and applied it to the docstring as well.

importlib._bootstrap._get_sourcefile().

Thanks to its only use by the C API, it was never properly tested
until now.

Thanks to Neal Norwitz for discovering the bug and Madison May for the patch.

Issue #12990: The "Python Launcher" on OSX could not launch python scripts that have paths that include wide characters.

The documentation does mention that the streams are opened in text mode
when univeral_newlines is true, but not that that they are opened in
binary mode when that argument is false and that seems to confuse at
least some users.

AIX maps the first page of memory at address zero as valid, read-only.  Reading
NULL is not a fault on AIX. This is utilized by IBM compiler optimizations.
One speculatively can indirect through a pointer which may be null without
first testing if null and defer the test before using the value.

when the function is called twice, so faulthandler.unregister() restores
correctly the original signal handler.

tstate is first removed from TLS and then deallocated.
CID 1019639 (#1 of 1): Use after free (USE_AFTER_FREE)
 use_after_free: Using freed pointer tstate.

segfault inside the _pickle C extension.

Patch by Tal Einat, Roget Serwy, and Todd Rovito.

Also change private dict used as a set to a set.

Issue #18224: Removed pydoc script from created venv, as it causes problems on Windows and adds no value over and above python -m pydoc ...

Idle code already uses x.delegate instead of x.getdelegate().
The printed report must have been for testing.

Patch by Vajrasky Kok, with slight modification to the tests by me.

replacing warnings.formatwarnings and to reverse replacement of
warnings.showwarnings when import is complete and when main function exits.
Add test_warning.py. Vinay Sajip provided capture_warnings function.

replacing redundant signature in input() docstring with one-line summary.
Original patch by Terrel Shumway.

There were no tests for the encoders module.  encode_base64 worked
because it is the default and so got tested implicitly elsewhere, and
we use encode_7or8bit internally, so that worked, too.  I previously
fixed encode_noop, so this fix means that everythign in the encoders
module now works, hopefully correctly.  Also added an explicit test
for encode_base64.