RFR: 7139770: MacOS JCK failures in DatagramSocket and MulticastSocket

[Michael McMahon]

Can I get the following webrev reviewed please?

http://cr.openjdk.java.net/~michaelm/7139770/webrev.1/

There are two issues. In DatagramSocket  the change uses the peekData()
api when available, instead of peek(), which in fact doesn't work at all
with our own PlainDatagramSocketImpl (it tries to compare InetAddress 
instances
with Inet4Addresses, which always fails, and it only supports IPv4)

In MulticastSocket I adjusted the recently added code which sets
a default interface. The default interface only needs to be set just prior
to joining a multicast group, and then only if an interface has not been 
set previously.

Thanks
Michael.