Load typedef headers if doing RNTuple I/O

This is RNTuple experimental I/O code - not affecting "normal" Athena but allowing to run RNTuple tests in LCG DEV3

Add forced loading of selected (currently 2) header files containing typedefs to builtin C++ types (not classes) because genreflex does not allow such typedefs in rootmap files so ROOT does not know were to find them on its own Hopefully a Temporary hack