SwTextBoxHelper::syncProperty: handle TextPreRotateAngle

For now only the most problematic -270 case, for which we don't have a
native writing direction: rotate the characters on a textportion level
instead.

CppunitTest_sw_ooxmlsdrexport's testFdo69636 is a reproducer for this,
the document model was fine already, but with this, the layout has the
rotation as well, as expected.

Change-Id: Iefc56f3adcea614566aaefd41d832d9b0cdb730b