Issue #18434: Updated example script in venv docs to use setuptools rather than Distribute.
#18431: Decode encoded words in atoms in new email parser.

There is more to be done here in terms of accepting RFC invalid
input that some mailers accept, but this covers the valid
RFC places where encoded words can occur in structured headers.
Merge heads.
Issue #18435: Replaced simple attribute container class Context with types.SimpleNamespace.
Merged upstream changes.
Issue #18434: Updated example script to tidy up resources.
Issue #18433: Clarified venv documentation.