Issue #14432: Document the removal of the PyFrameObject.f_tstate field
Issue #19946: Raise ImportError when the main module cannot be found
by multiprocessing.spawn (before it was raising an AttributeError).
#18036: update .pyc FAQ entry in light of PEP 3147.

Initial patch by Phil Connell.
Merge: #18036: update .pyc FAQ entry in light of PEP 3147.
Issue #19963: Document that importlib.import_module() will import
parent packages automatically.
merge for issue #19963
Issue #19704: Port test.test_threaded_import to PEP 451
#19975: remove unused imports from webbrowser module.

Report and patch by Claudiu Popa.
#19970: Fix some comment typos.

Report and patch by Vajrasky Kok.
Merge: #19970: Fix some comment typos.