State correct usage of literal examples in man pages in the coding standards

State correct usage of literal examples in man pages in the coding standards

The man pages contain inconsistent usage of backticks vs. single quotes
around options, commands, etc. that are in paragraphs. This commit states
that backticks should always be used around literal examples.

This commit states that "--" and friends should not be escaped
(e.g. use `--pretty=oneline` instead of `\--pretty=oneline`).

This commit also states correct usage for typesetting command usage
examples with inline substitutions.

Thanks-to: Ramkumar Ramachandra <artagnon@gmail.com>
Thanks-to: Stuart Rackham <srackham@gmail.com>
Thanks-to: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Jason St. John <jstjohn@purdue.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>