RFR(s): 8208641: SSLSocket should throw an exception when configuring DTLS

[Anthony Scarpino]

I need a review of this fix.  Simple change to throw an 
UnsupportedOperationException using SSLSocket with DTLS.  Additionally 
use SSLEngine for some of the generic methods that were defaulting to 
SSLSocket  This is only for the JSSE provider.

http://cr.openjdk.java.net/~ascarpino/8208641/webrev/
Tony