BzzOdeStiff class

The following additional check has been inserted in the BzzOdeStiff class to verify the Jacobian accuracy. 

The object of of the BzzOdeStiff class, which can tackle stiff problems, needs 115 evaluations of the system for integration between 0 and 0.01, whereas 271 evaluations are needed for integration between 0 and 100. 

The BzzOdeNonStiffObJect and BzzOdeStiffObJect classes are different from the previous BzzOdeNonStiff and BzzOdeStiff classes because their objects are initialized with an object rather than the name of the function. Consider the previous example OdeNonStiffl. Now the program is... 

In the BzzOdeStiff classes, the functions GetTimelnMeshPoint and GetYInMeshPoint allow us to get the values of t and y at each mesh point used in the integration procedure. 

The integration step for BzzOdeStiff or BzzOdeNonStifT classes is disjoined from the user s need to know the values at certain specific points. Thus, if the frmction to be zeroed is monotone, it will suffice to monitor its value in the mesh points dimng integration and, when it changes sign, to use an object from the BzzFunctionRoot class to refine the root. 

In the BzzMath library, the BzzOdeStiff and BzzOdeSparseStlff classes contain several functions that make it easy to move from a system to another one of different nature. 

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