CppunitTest_sw_ooxmlexport: make it possible to use ..._TEST_ONLY with -Werror

Change-Id: I451f81495a8e8535c8e0194198602ee5732164c6
DOCX import: tblHeader implies firstRow

If a table row is marked as tblHeader, then the firstRow section of the
table style should be applied, even if that row is in fact not the first
row.

Change-Id: I10605f404160e72c620e9204503203fea1c6d6d8