Although 2013 commit 60ec497e
added support for the other tcMar items, it omitted _start and
_end (perhaps because they caused unit test failures).
The document in bug 78508 proves that these are needed.

Testing whether the cell spacing matches the default table
spacing should occur before adjusting for MSO compatibility.
This fixes the three unit tests that mysteriously failed
when adding _start/_end support.

Unfortunately, these two fixes could not be committed
separately - the unit test fails unless both parts
are included. I couldn't figure out why.

Change-Id: I9507da48b629b9618c5ee790bf0088ce82fc5692
Reviewed-on: https://gerrit.libreoffice.org/43432Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>