Fix treatment of standalone tags.

Lines containing ^, /, !, <, or = tags should be stripped from the
output if the tags are standalone. The least intrusive way to handle
this I could find was to simply "expand" the endpoints of such tags
to fill the line - all existing logic will continue to just work.

This fixes 29 spec test failures.
Fix Doxygen syntax.

It's @p to reference a parameter, not @a.
Reduce the number of expandTag(..) call sites.
Make expandTag(..) static.
Follow code style convention for & position.
Merge pull request #15 from estan/standalone-tags

Fix treatment of standalone tags.