Attempt to use giac for JUnit testing (untested)


git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@25796 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
Fix for PreviousPrime[-10] in GIAC

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@25797 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
Fix for PreviousPrime[2] in GIAC

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@25798 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e