zero various members

(cherry picked from commit 9de20d1eb046f7bb92d893408206b91a9c054e2e)

Conflicts:
	filter/Module_filter.mk
	filter/source/graphicfilter/ipcx/ipcx.cxx
	filter/source/graphicfilter/itiff/itiff.cxx

Change-Id: Iad6948fdf6eb60f86d764783b72a4fe7f5642e40
Reviewed-on: https://gerrit.libreoffice.org/9082
Tested-by: Markus Mohrhard <markus.mohrhard@googlemail.com>
Reviewed-by: Markus Mohrhard <markus.mohrhard@googlemail.com>