RFR[8241072]: 'Reimplement Legacy DatagramSocket API'

[Patrick Concannon]

This is a request for review for the implementation changes for JEP 373: 
'Reimplement Legacy DatagramSocket API' [1]. A CSR has also been created 
[2].

The implementation of JEP 373 can be viewed on the JDK-8230211-branch in 
the sandbox [3].

A link to the webrev with the cumulated changes is available below [4].

The sources changes are limited to five files. The webrev also adds 
additional tests while a selection of existing tests have been updated 
to run with both the old and new implementation. Please refer to the JEP 
[1] for more information.

-Patrick


[1] https://openjdk.java.net/jeps/373

[2] https://bugs.openjdk.java.net/browse/JDK-8241188

[3] http://hg.openjdk.java.net/jdk/sandbox/shortlog/8176cc48cc78

[4] http://cr.openjdk.java.net/~pconcannon/8241072/webrevs/webrev.00/