function H=level(func,x0,dxmax,col,precision,kmax); C. Gonzaga, 6-dec-1999. traces a level curve for objetive through x0. The curve closes (result=1) or k reaches kmax or |x-x0|>dxmax componentwise (result 0). Normal call: result=level(func,x0,dxmax) col is a color letter, default 'r'. if precision is zero or not given, precision=1 is used. ----> normal precision is 1. High precision: precision=10. ----> low precision: precision in the interval 0.1,1. if kmax is not given, uses kmax=500. Returns a cell of handles for the newly created graphic objects.