tidying

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@24814 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
[giac] improved parsing of surd(x,2)-> sqrt(x), surd(x,3)-> cbrt(x)

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@24815 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e