Fix Issue #529: Test for 64bit OS, plus consequential documentation changes

- [x] Is it mergable
- [x] Did it pass the tests?
- N/A If it introduces new functionality in scripts/ is it tested?
  Check for code coverage.
- [x] Is it well formatted? Look at `pep8`/`pylint`, `cppcheck`, and
  `make doc` output. Use `autopep8` and `astyle -A10 --max-code-length=80`
  if needed.
- N/A Is it documented in the Changelog?
- [x] Was spellcheck run on the source code and documentation after changes
  were made?
I would say "64-bit operating system". Let's capitalize the 'P' in Python in the second sentence while we're at it as well.