Resolves: i124608 when exporting selection...

use selection boundrect as svg canvas

(cherry picked from commit bfc1aa46b9ee9ad37728389eb636fc9fb5b9827f)

Conflicts:
	filter/source/svg/svgexport.cxx
	filter/source/svg/svgfilter.cxx
	filter/source/svg/svgfilter.hxx

Change-Id: Ib10e785ebb611f0e33ea3ae799dfea20b05d250a