* Improved venv docs to note that isolation is the default.

* Insert "that" so that a sentence reads better.

* Improved wording.

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Co-authored-by: Vinay Sajip <vinay_sajip@yahoo.co.uk>

Provide a stub implementation of umask that is enough to get some tests passing.
More work is needed upstream in Emscripten to make all umask tests to pass.

Makes the Emscripten stack overflow skip message consistent with WASI, 
and replaces some ad-hoc skips.

…#136707)

This might have been fixed by gh-136624, or by some Emscripten change.
In any case, it no longer seems to be needed.

…-136704)

`_asyncio` is now built as a static module so that thread states can be accessed directly via registers and avoids the overhead of function call.