Update to check for new function header doc standards

In #502190: Hook implementation headers out of compliance with standards, the community agreed on a new set of standards for function headers, and especially for hook implementation function headers. These standards are detailed on the Doxygen formatting conventions Handbook page.

The coder module needs to be updated to check for these standards. In particular, an 80-character limit on the brief function description, which should end with a period and be followed by a blank line. Comment http://drupal.org/node/502190#comment-1818202 mentions that the Coder Tough Love module already checks these, so that code could be grabbed for Coder.