RFR: 8260428: Drop support for pre JDK 1.4 DatagramSocketImpl implementations [v3]

[Patrick Concannon]

> Hi,
> 
> Could someone please review my changes (and CSR) to drop support for pre JDK 1.4 `DatagramSocketImpl` implementations?
> 
> These changes propose to drop support for `DatagramSocketImpls` that were compiled with JDK 1.3 or older, which do not have support for connected sockets, for peeking at received datagrams, and for joining and leaving a group at a specific interface. This support is legacy, and should be relatively safe to remove as such implementations do not compile with JDK 1.4 or newer.
> 
> Finally, with this set of proposed changes, if you have an `oldImpl`, and don’t use connect, then the methods `joinGroup` and `leaveGroup` will throw `NoSuchMethodError`.  However, the current behaviour in `DatagramSocketImpl` is to throw an `UnsupportedOperationsException` for a method not implemented. Should this set of changes update the `joinGroup` and `leaveGroup` methods in order to preserve this behaviour?
> 
> CSR: https://bugs.openjdk.java.net/browse/JDK-8274633
> 
> Kind regards,
> 
> Patrick

Patrick Concannon has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains four additional commits since the last revision:

 - Merge remote-tracking branch 'origin/master' into JDK-8260428
 - 8260428: Corrected javadoc typos; combined declaration and initialization of variables in DSI; refactored dummy impls in test
 - Merge remote-tracking branch 'origin/master' into JDK-8260428
 - 8260428: Drop support for pre JDK 1.4 DatagramSocketImpl implementations

-------------

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/5887/files
  - new: https://git.openjdk.java.net/jdk/pull/5887/files/67265bd4..0a920f65

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=5887&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=5887&range=01-02

  Stats: 24453 lines in 567 files changed: 18562 ins; 3958 del; 1933 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5887.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5887/head:pull/5887

PR: https://git.openjdk.java.net/jdk/pull/5887