deprecated "\O" notation occurs in diffusion example

[Stephen Siegel]

The following assertion occurs in diffusion_seq.mmp:

 assert forall {int i | 1 <= i && i <= nx-2} v_new[i] - 
    ( (u(i*dx,(iter+1)*dt) - u(i*dx,iter*dt))/dt - 
    k*( (u((i+1)*dx,iter*dt) - 2*u(i*dx,iter*dt) + u((i-1)*dx,iter*dt))/dt)) == \O(dx*dx)+\O(dt);

See my grant proposal document for the correct assertion.

Make sure the \O does not occur in other examples as well.

[zirkel]

Changed.