CPP11 — Fixed-point initialization

Summary: The Fixed mapping requires throwing DATA_CONVERSION if a value has more
than 31 integral digits:

Fixed f = 1E32; // DATA_CONVERSION

This raises the question of how to deal with Fixed types in environments
without C++ exceptions. Presumably, we need to add a CORBA::Environment
parameter everywhere. Unfortunately, that isn"t possible with the overloaded
operators that are currently defined.