That file creates a global (static const) object that:
- at its creation (start of the program), it stores the FPU rounding mode,
- at its destruction (end of the program), it emits a CGAL_warning is the
current rounding mode is different from the stored one.
That will permit to track if all CGAL kernel code restore the FPU rounding
mode correctly (needed for some CGAL user and GeometryFactory customers).