Compaq C 6.2 for VMS will complain when we want to convert

Compaq C 6.2 for VMS will complain when we want to convert
non-function pointers to function pointers and vice versa.
The current solution is to have unions that describe the
conversion we want to do, and gives us the ability to extract
the type of data we want.

The current solution is a quick fix, and can probably be made
in a more general or elegant way.