fix for #3206 ($6 not working in CAS)

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@25728 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
4.9.138.0

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@25729 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
#3192 Event handling revisited

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@25730 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
Do not repaint the GV with a graphics unless necessary, use simple fillRect instead.

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@25731 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
[giac] more fixes

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@25732 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e