convert them to pointers. If they're zero, they're converted (to
NULL pointers) regardless of size. If they're non-zero, they can't
be converted (without a cast). This matches the behavior of other
version of lint, e.g. the lints on Digital UNIX and HP-UX.
* recognize that pointers to identical unnamed and untyped structs,
unions, and enums are, in fact, identical. This is done by tagging
each of unnamed and untyped structure, union and enum with a unique
position of creation, which is used as a unique identifier that
when determine whether or not a pair of structures, unions, or enums
are identical.