Check the algorithm name / oid for PRIVATEDNS and PRIVATEOID signatures.

The fromwire and fromtext methods need to check that there are well formed algorithm names / oids in SIG and RRSIG records for algorithms 253 and 254 respectively. These checks are the same as have already been applied to KEY, DNSKEY etc.

A.1.1.  Private Algorithm Types

   Algorithm number 253 is reserved for private use and will never be
   assigned to a specific algorithm.  The public key area in the DNSKEY
   RR and the signature area in the RRSIG RR begin with a wire encoded
   domain name, which MUST NOT be compressed.  The domain name indicates
   the private algorithm to use, and the remainder of the public key
   area is determined by that algorithm.  Entities should only use
   domain names they control to designate their private algorithms.

   Algorithm number 254 is reserved for private use and will never be
   assigned to a specific algorithm.  The public key area in the DNSKEY
   RR and the signature area in the RRSIG RR begin with an unsigned
   length byte followed by a BER encoded Object Identifier (ISO OID) of
   that length.  The OID indicates the private algorithm in use, and the
   remainder of the area is whatever is required by that algorithm.
   Entities should only use OIDs they control to designate their private
   algorithms.