Use "real" reStructuredText comments instead of using the "raw" directive.

See <http://docutils.sourceforge.net/docs/user/rst/quickref.html#comments

>.

Thanks to Chris Lamb and edb01aa2f in diffoscope.git and to Mattia for
pointing me to it.

Signed-off-by: Holger Levsen <holger@layer-acht.org>