Support for if equations inside when equations

[Adrian Pop]

Currently the back-end cannot fully handle if equations inside when equations.
It can only handle if equations that can be transformed to if expressions.
So this kind of equations do fail in the back-end

when wE43_direct.switchingDynamics.ReachMiddle then
  if abs(wE43_direct.switchingDynamics.x_d) > wE43_direct.switchingDynamics.transVel 
  then
    reinit(wE43_direct.switchingDynamics.x_d,wE43_direct.switchingDynamics.coefficientOfDamping * pre(wE43_direct.switchingDynamics.x_d));
    wE43_direct.switchingDynamics.targetReached = false;
  else
    wE43_direct.switchingDynamics.targetReached = true;
    reinit(wE43_direct.switchingDynamics.x_d,0.0);
    reinit(wE43_direct.switchingDynamics.x,0.0);
  end if;
end when;