Ocaml binding update, add fast math optimisation flags to a FMOperator.

Since I did not find a way to create Fast math flag with the ocaml binding, i updated the llvm ocaml binding to permit such operations. With 3-4 functions in llvm.ml and a product type. In the cpp side I add in Core.cpp 4-5 functions to make support for the binding.

These optimisations are very important for my work, wish that will help anybody else.