Rename MATH class

[bandurvp]

When the VDM MATH library is generated, the names of the resulting header file clashes with standard Widnows files. Recommend that a refactoring be done before code generation to rename this class to VdmMathLib or something similar. It must not be renamed MATHLib, as this would clash with the runtime support counterpart.

[bandurvp]

I have just looked into whether it would be worthwhile to quickly hack it such that it only renames the header file and the corresponding #include line in the class .c file, but it seems to be more trouble than it's worth due to the structure of the generator. I think a refactoring transformation that renames MATH as above would be the most elegant solution, especially since it can be toggled, should this become relevant.