Using SwTableFormatCmp in loops with SwTableLine::ChgFrameFormat, where
the latter may delete the old format of a frame, may invalidate the pOld
of a SwTableFormatCmp, and lead to use-after-free. To avoid this, let's
register SwTableFormatCmp as the old format writer listener.

Also use unique_ptr in vectors to simplify memory management.

Change-Id: I5ac93f4c3ae549b79a41220bda880386dd529c36
Reviewed-on: https://gerrit.libreoffice.org/55653
Tested-by: Jenkins
Reviewed-by: Michael Stahl <Michael.Stahl@cib.de>