doxygen gets all hung up about a failed markup and doesn't produce any
kind of reasonable output.
Merge pull request #149 from bangerth/fix-changelog

doxygen gets all hung up about a failed markup and doesn't produce any kind of reasonable output.
Doxygen wants the title of a page to be on a single line, or it will just forget the rest.
Merge pull request #150 from bangerth/fix-older-changelogs

Doxygen wants the title of a page to be on a single line, or it will jus...