RFR: 8260338: Some fields in HaltNode is not cloned

[Yasumasa Suenaga]

I got strange log as following. Contents in `CodeString` is garbled. It seems not to be initialized.

[3.155s][trace][codestrings ] Created CodeString [ dｴ・] (0x7f3804a150)

`HaltNode` has two fields - `_reachable` and `_halt_reason`, but they would not be cloned at Node::clone.

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Commit messages:
 - 8260338: Some fields in HaltNode is not cloned

Changes: https://git.openjdk.java.net/jdk/pull/2213/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=2213&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8260338
  Stats: 10 lines in 3 files changed: 7 ins; 0 del; 3 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2213.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2213/head:pull/2213

PR: https://git.openjdk.java.net/jdk/pull/2213