RFR: 8284890: Support for Do not fragment IP socket options [v8]

[Michael McMahon]

> Hi,
> 
> Could I get the following PR review please? It adds a new JDK specific extended socket option
> called IP_DONTFRAGMENT, which disables IP packet fragmentation in both IPv4 and IPv6
> UDP sockets (NIO DatagramChannels). For IPv4 in particular, it sets the DF (Dont Fragment) bit
> in the IP header. There is no equivalent in the IPv6 packet header as fragmentation is implemented
> exclusively by the sending and receiving nodes.
> 
> Thanks,
> Michael

Michael McMahon has updated the pull request incrementally with one additional commit since the last revision:

  test update

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/8245/files
  - new: https://git.openjdk.java.net/jdk/pull/8245/files/428a9801..e6b12eb8

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=8245&range=07
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=8245&range=06-07

  Stats: 20 lines in 1 file changed: 2 ins; 17 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8245.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8245/head:pull/8245

PR: https://git.openjdk.java.net/jdk/pull/8245