cast to dns_rdatatype_t via macros of their same name
                        so that they are of the proper integral type wherever
                        a dns_rdatatype_t is needed.

(And a few prototypes that I recently bogusly changed to take "int" parameters
in place of "dns_rdatatype_t" to accomodate the type of an enum identifier
have been reverted to again properly take a dns_rdatatype_t.)