Xls Writer Parser Handle Boolean Literals as Function Arguments

[oleibman]

Fix #3369. The parser had failed to account for TRUE and FALSE when supplied as arguments to a function.

I had hoped to be able to do something about its inability to handle defined names as well. I failed. I think another section might need to be added to the Writer output which specifies the defined names. I haven't yet located any suitable documentation.

This is:

• 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
• Code style is respected
• 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?

Provide an explanation of why this change is needed, with links to any Issues (if appropriate).
If this is a bugfix or a new feature, and there are no existing Issues, then please also create an issue that will make it easier to track progress with this PR.

[oleibman]

Not concerned with Scrutinizer "complexity" complaint.