[giac] various fixes

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@24640 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
[giac] removing hacks (not needed any more)

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@24641 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
[giac] updating unit tests

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@24642 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
[giac] replace(/lower_incomplete_gamma/g,'lowerincompletegamma');

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@24643 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e