implement Extremum for If[0<x<10,f]

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@37952 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
#4585 fixed

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@37953 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e