* Make the error variable always named err.
Sometimes the error variable was named 'err' sometimes 'e'. Sometimes
'e' refered to an EDNS or string and not an error type.
* Use t.Errorf instead of t.Logf & t.Fail.
This will allow RRSIG.Sign to use generic crypto.Signer implementations.
This is a interface breaking change, even if the required changes are most
likely just type asserions from crypto.PrivateKey to the underlying type or
crypto.Signer.
Pavel Odintsov
Michael Haro
Filippo Valsorda
Mart Roosmaa
Miek Gieben