fix test failures introduced by a22d8a2eb0e5 * scripts/ode/private/integrate_adaptive.m: fix stepping backwards, fix invocation of OutputFcn, fix text of some error messages * scripts/ode/private/integrate_const.m: remove use of option OutputSave * scripts/ode/private/integrate_n_steps.m: remove use of option OutputSave

# u_vr.m

## define and exectute "__demo__" once
eval ("function __demo__ ();  df_vr;  v = vr * 2; endfunction");
__demo__;

## clear definition of "__demo__"
clear __demo__

## define and exectute "__demo__" once more
eval ("function __demo__ ();  df_vr;  v = vr * 2; endfunction");
__demo__;