[giac] exact ChiSquare, fix for Numeric[x + x/2]

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@24818 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
Changing giac.js to the latest version in web/kickstart.xml

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@24819 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
[giac] updated unit tests

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@24820 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e