RFR: 8280832: Update usage docs for NonblockingQueue [v3]

[Kim Barrett]

> Please review this update of the usage and implementation comments for
> NonblockingQueue to discuss the ABA issue in push/append operations.

Kim Barrett has updated the pull request incrementally with one additional commit since the last revision:

  dholmes review

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/7393/files
  - new: https://git.openjdk.java.net/jdk/pull/7393/files/fe7cc130..7aacc083

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=7393&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=7393&range=01-02

  Stats: 7 lines in 1 file changed: 3 ins; 0 del; 4 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7393.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7393/head:pull/7393

PR: https://git.openjdk.java.net/jdk/pull/7393