update lib dns++ python tools
#1880 (closed) showed that even they still work the python tools used for the dns++ library should be updated:
- src/lib/dns/gen-rdatacode.py complains about a not existing (BTW for a long time) file in a not existing (this point triggers the error) src/lib/dns/python directory. IMHO the corresponding code is obsolete i.e. implements a feature which has not been used since a lot of years if it was used one day...
- src/lib/util/python/gen_wiredata.py triggers a warning with python3. I added a comment at the corresponding line of code.
The documentation should be updated too: for the first script it is in the s-rdatacode entry of the Makefile. The second is in a commented entry of the src/lib/dns/tests/testdata Makefile and requires to be called in the UTC timezone when timestamps are generated as for RRSIG or TKEY RRs (I used with success the TZ environment variable).