GSSAPI tests and fixes
* Fixed AbstractGssapiMechanism.DEFAULT_MAX_BUFFER_SIZE (3 octets)
* Fixed bugs in networkOrderBytesToInt() and intToNetworkOrderBytes()
* ChallengeResponseState should return byte[0] instead of null
* SecurityLayerAdvertiser: gssContext.getWrapSizeLimit() moved on the
   opposite side of communication
* getNegotiatedProperty now returns Strings