[giac] simplifying serialization of (1,2)+(3,4)

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@28025 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
#3563 fix - may cause test failures

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@28026 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e