speed up data hashcodes

core/java/src/net/i2p/data/Destination.java

core/java/src/net/i2p/data/Hash.java

core/java/src/net/i2p/data/LeaseSet.java

core/java/src/net/i2p/data/PrivateKey.java

core/java/src/net/i2p/data/PublicKey.java

core/java/src/net/i2p/data/RouterAddress.java

core/java/src/net/i2p/data/RouterIdentity.java

core/java/src/net/i2p/data/SessionKey.java

core/java/src/net/i2p/data/Signature.java

core/java/src/net/i2p/data/SigningPrivateKey.java

core/java/src/net/i2p/data/SigningPublicKey.java