RFR: 8282917: Remove InetAddressImplFactory from InetAddress [v4]

[Aleksei Efimov]

> Hi,
> 
> This cleanup change removes `InetAddressImplFactory` class from `InetAddress`. The list of changes:
> - Remove `InetAddressImplFactory` from `InetAddress`
> - Since `isIPv6Supported` native code is identical for Windows and Unix implementations it was moved to the libnet's `InetAddress.c`.
> - `InetAddressImplFactory.c` Windows and Unix implementations were removed
> 
> Testing: jdk-tier1 to jdk-tier3 tests show no failures related to the change

Aleksei Efimov 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 five additional commits since the last revision:

 - Merge branch 'master' into JDK-8282917_Remove_InetAddressImplFactory
 - Update Java_java_net_InetAddress_isIPv4Available signature comment
 - Address review comments
 - Merge branch 'master' into JDK-8282917_Remove_InetAddressImplFactory
 - 8282917: Remove InetAddressImplFactory from InetAddress

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/7842/files
  - new: https://git.openjdk.java.net/jdk/pull/7842/files/0b75bb45..77d0664f

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=7842&range=03
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=7842&range=02-03

  Stats: 7722 lines in 1062 files changed: 3843 ins; 1584 del; 2295 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7842.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7842/head:pull/7842

PR: https://git.openjdk.java.net/jdk/pull/7842