STYLE: fix spelling, backslashes etc. in codingStyleGuide.org

- now passes through LaTeX with fewer complaints.

- added note about braces for 'case' statements.

- could not formulate a sensible rule about when return statements
  need parentheses and when not.

- did not update codingStyleGuide.pdf ... I don't even know if it
  should be part of the git repo at all