CAS improvement

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@23061 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
Fix for GCD, LCM in CAS [needs backport]

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@23062 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e