sw: remove references to ODF_COMMENTRANGE

Fieldmarks of type ODF_COMMENTRANGE are no longer used, since we got
annotation marks.

Also remove two unit tests: they tested problems which are no longer
possible by design (commented text ranges are no longer fieldmarks, and
there is a single placeholder character for them, instead of 3).

Change-Id: I14bf144c436329d2aa8c48493e5ad87db862cceb
xmloff: unused define

Change-Id: I77d072b3b6b9b7d86e6279a5cae3d96a21827eb2