RFR: 8290036: Define and specify Runtime shutdown sequence [v3]

[Stuart Marks]

> Initial edits to addShutdownHook from Alex.
> 
> See [JDK-8290036](https://bugs.openjdk.org/browse/JDK-8290036).

Stuart Marks has updated the pull request incrementally with one additional commit since the last revision:

  More updates after discussion with Alex.

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/9437/files
  - new: https://git.openjdk.org/jdk/pull/9437/files/b23a7321..5a16ea30

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=9437&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=9437&range=01-02

  Stats: 61 lines in 2 files changed: 18 ins; 1 del; 42 mod
  Patch: https://git.openjdk.org/jdk/pull/9437.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9437/head:pull/9437

PR: https://git.openjdk.org/jdk/pull/9437