remove workarounds for https://code.google.com/p/google-web-toolkit/issues/detail?id=4097 (GWT bug fixed in 2.6 cast StringBuilder)

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@36204 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
bugfix for freehand polygons

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@36205 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e