PEP 757: misc edits

[skirpichev]

• Change is either:
  • To a Draft PEP
  • To an Accepted or Final PEP, with Steering Council approval
  • To fix an editorial issue (markup, typo, link, header, etc)
• PR title prefixed with PEP number (e.g. PEP 123: Summary of changes)

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📚 Documentation preview 📚: https://pep-previews--3984.org.readthedocs.build/

[skirpichev]

This mostly factor out code to query layout parameters; sync with gmpy2.

[hugovk]

By the way, you can run make spellcheck to look for typos. From main:

peps/pep-0757.rst:392: Currenly ==> Currently
peps/pep-0757.rst:396: aribitrary ==> arbitrary

[vstinner]

Merged, thanks.