Update XMLWriter.php: htmlspecialchars use Settings::htmlEntityFlags

[cscrewsandcaptains]

XLSX files are now saved cell content with apros as >>'<< and not longer as '

This is:

• [ x ] a bugfix
• a new feature
• refactoring
• additional unit tests

Checklist:

• Changes are covered by unit tests
  • Changes are covered by existing unit tests
  • New unit tests have been added
• [ x ] Code style is respected
• [ x ] Commit message explains why the change is made (see https://github.com/erlang/otp/wiki/Writing-good-commit-messages)
• CHANGELOG.md contains a short summary of the change and a link to the pull request if applicable
• Documentation is updated as necessary

Why this change is needed?

Export XLSX and use this in R, than the content of the cells are wrong, becaues ' and not ' is used. See Issue #4537

[oleibman]

As you can see in the linked issue, I am skeptical about your use case. But, for now, can you please add a formal test which would fail without your change but will succeed with it?

[oleibman]

Superseded by PR #4540. Converting this PR to draft. It will be closed if 4540 is merged, or reopened if 4540 is dropped.