[lworld] RFR: 8280456: [lworld] javac should allow compilation with abstract java.lang.Object class

[Srikanth Adayapalam]

- Warn on attempt to instantiate Object
    - If j.l.O is seen as abstract, don't complain about abstract class instantiation
    - Reroute instantiation to calls of java.util.Objects.newIdentity
    - Extend treatment to both constructor invocations and constructor references.

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Commit messages:
 - 8280456: javac should allow compilation with abstract java.lang.Object class

Changes: https://git.openjdk.java.net/valhalla/pull/616/files
 Webrev: https://webrevs.openjdk.java.net/?repo=valhalla&pr=616&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8280456
  Stats: 68 lines in 5 files changed: 66 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/valhalla/pull/616.diff
  Fetch: git fetch https://git.openjdk.java.net/valhalla pull/616/head:pull/616

PR: https://git.openjdk.java.net/valhalla/pull/616