RFR: 8305089: [AIX] Implement missing socket options on AIX

[Varada M]

Breaking this into two parts : 

1. Implementing socket options for AIX 
2. DontFragmentTest failure 

- Implementing socket options for AIX :

Unlike the linux, windows and macOS, AIX uses the default implementation for socket options such as ipDontFragmentSupported(), keepAliveOptionsSupported(), setTcpkeepAliveProbes, getTcpkeepAliveProbes, setQuickAck, getQuickAck and more, where it either returns false or exception. These options can be implemented on AIX with the supported flags like SO_PEERID, TCP_NODELAYACK is the equivalent AIX option for TCP_QUICKACK and IPPROTO_TCP, IP_DONTFRAG. 

- DontFragment test failure :

DontFragmentTest.java fails with a runtime exception : “IP_DONTFRAGMENT should be supported” because the supportOptions doesn’t contain IP_DONTFRAGMENT flag.

Reported Issue :  [JDK-8305089](https://bugs.openjdk.org/browse/JDK-8305089)

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Commit messages:
 - AIX socket options
 - aix socket options
 - AIX Socket Options

Changes: https://git.openjdk.org/jdk/pull/13240/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13240&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8305089
  Stats: 411 lines in 4 files changed: 410 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/13240.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13240/head:pull/13240

PR: https://git.openjdk.org/jdk/pull/13240