Initialisation almost succeeds. nil and t are successfully instantiated.

We then go into a mess of exceptions which trigger exceptions until we run out
of allocatable memory, but all those exceptions and stack frames are correctly
allocated and torn down again afterwards, so.... sort of good?

src/c/payloads/psse_string.h

@@ -33,8 +33,6 @@ struct string_payload {
     struct pso_pointer cdr;
 };
 
-struct pso_pointer make_string( wint_t c, struct pso_pointer tail );
-
 struct pso_pointer destroy_string( struct pso_pointer fp,
                                    struct pso_pointer env );