Cleanup2

Created by: germasch

So hopefully, this is one is actually non-controversial

• Move the implementation of struct TypeInfo into ADIOSTypes.inl, following the standard practices for the project. It also puts struct FixedWidthInt into an anonymous namespace, which arguably doesn't do much. I can undo that part if you prefer.
• Fixed (eliminated) the last use of the primitive - stdint mapping within the core of adios, which is already using all stdint-based types, so that one piece of mapping already is an identity map that can be removed.