The documentation for CInterface says among many other things:
We would like to convert C-enumerations like colour into an equivalent ML datatype, together with functions to convert between values of the datatype and ML integers. This can be achieved automatically by using the script proc-enums, contained in the scripts subdirectory of the source tree.
I don't see any such script anywhere in the tarballs from which I built PolyML: driver, mlsource, or basis. In fact, if I should believe "locate" it isn't anywhere on my machine :) Where oh where is it hiding?