Issue #19218: set __name__ of _collections_abc to collections.abc in order to fix tests and keep beautiful qualified names.

This does not fix #19227, but should stop the Gentoo buildbot from hanging.

emulation has changed from 0-based indexing to 1-based like gnu readline.
Original patch by Ronald Oussoren.

("make smelly" now clean)

failed, second invocation of close() and destructor no more raise an
exception.

Initial wording proposed by John Roth.

Closes #19179: make table of XML vulnerabilities clearer by using "everyday" booleans and explaining the table beforehand.