RFR: 8193559: ugly DO_JAVA_THREADS macro should be replaced [v3]

[Daniel D.Daugherty]

> This is a simple rewrite of what is "Possibly the ugliest for loop the world has seen."
> Thanks to @stefank for the draft proposed fix. Thanks to @fisk for providing this
> piece of history that I'm finally getting around to cleaning up. While this macro has
> been with us for a long time, its time has passed...
> 
> Tested with Mach5 Tier[1-3].

Daniel D. Daugherty 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 three additional commits since the last revision:

 - Merge branch 'master' into JDK-8193559
 - kbarrett CR - delete unused _list member.
 - 8193559.cr0

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/4671/files
  - new: https://git.openjdk.java.net/jdk/pull/4671/files/5ee49914..a133ca42

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=4671&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=4671&range=01-02

  Stats: 39768 lines in 1046 files changed: 18045 ins; 16146 del; 5577 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4671.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4671/head:pull/4671

PR: https://git.openjdk.java.net/jdk/pull/4671