6935563: (dc) Improve connection reset/port unreachable handling [win

[Alan Bateman]

Chris - would you mind looking at this one? It's a Windows specific 
issue that rises with unconnected datagram channels when an ICMP 
destination unreachable message is received. As the channel is 
unconnected then the message should be dropped and shouldn't cause a 
Selector to wakeup. In order to get the expected behavior we need to use 
the SIO_UDP_CONNRESET control code to toggle whether we receive the 
connection reset error or not. The changes are very simple and the 
webrev is here:
   http://cr.openjdk.java.net/~alanb/6935563/webrev/

Thanks,
Alan.