Matching fails after Dummy Derivative Method in some case

[wbraun]

For the following example we need a restart of the matching, due to incorrect implementation of matching algorithm.
The problem results in a lack of equations of the strong components and then missing of equations while the simulation.

model test
  Real x(start=1),y(start=0);
  Real xd,yd;
  Real Foo;
equation
  x*x+y*y=1;
  der(y)=yd+sin(time);
  der(x)=xd+sin(time);
  der(xd) = -x*Foo;
  der(yd) = -Foo*y;
end test;