Support for dnsjava 3

[mwullink]

dnssecjava is not compatible with the changed api of dnsjavva 3

it results in the following error.

java.lang.NoSuchMethodError: 'org.xbill.DNS.RRset[] org.xbill.DNS.Message.getSectionRRsets(int)'
at org.jitsi.dnssec.SMessage.(SMessage.java:114)
at org.jitsi.dnssec.validator.ValidatingResolver.sendRequest(ValidatingResolver.java:675)
at org.jitsi.dnssec.validator.ValidatingResolver.send(ValidatingResolver.java:1219)

[ibauersachs]

Thanks, I'm already working on that. Unfortunately Mockito/Powermock seems to have a bug/"feature" that I'm now running into and makes the unit tests fail.