Reduce nonlinear system of equations in radiator model

[mwetter]

In Dymola 2016 FD01, the nonlinear system of equation for the radiator model RadiatorEN442_2 increased compared to Dymola 2016. An isssue has been filed with dassault. This ticket is to implement a work-around received from Dassault.

[mwetter]

The commit 223a809 changes the statistics as follows:
Before the change

Sizes of linear systems of equations: {2, 2, 2, 2, 2}
Sizes after manipulation of the linear systems: {0, 0, 0, 0, 0}
Sizes of nonlinear systems of equations: {1, 1, 50}
Sizes after manipulation of the nonlinear systems: {0, 0, 5}
Number of numerical Jacobians: 0

Initialization problem
Sizes of nonlinear systems of equations: {21, 21, 1, 1, 50}
Sizes after manipulation of the nonlinear systems: {11, 11, 1, 1, 5}
Number of numerical Jacobians: 0

After the change

Sizes of linear systems of equations: {2, 2, 2, 2, 2}
Sizes after manipulation of the linear systems: {0, 0, 0, 0, 0}
Sizes of nonlinear systems of equations: {1, 1, 50}
Sizes after manipulation of the nonlinear systems: {0, 0, 5}
Number of numerical Jacobians: 0

Initialization problem
Sizes of nonlinear systems of equations: {11, 11, 1, 1, 50}
Sizes after manipulation of the nonlinear systems: {5, 5, 1, 1, 5}
Number of numerical Jacobians: 0