RFR: 8229517: Support for optional asynchronous/buffered logging [v10]

[Xin Liu]

> This patch provides a buffer to store asynchrounous messages and flush them to
> underlying files periodically.

Xin Liu has updated the pull request incrementally with three additional commits since the last revision:

 - Implement the global option -Xlog:async per CSR.
   
   The old options -XX:+AsyncLogging and the output option are both removed.
   This patch also deliver the zero-cost promise. ie. No AsyncLog thread will be
   launched if async_mode is not eanbled.
 - Reimplement Accurate Decorations for AsyncLogging.
   
   LogDecorations defines a copy constructutor. Each log message copys it
   once.
 - Revert "Accurate Decorations for AsyncLogging."
   
   This reverts commit 1f06be3126f829055aff3720aea7e82544fd0c3a.

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/3135/files
  - new: https://git.openjdk.java.net/jdk/pull/3135/files/e2d6f9e0..98ae33fb

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=3135&range=09
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=3135&range=08-09

  Stats: 265 lines in 12 files changed: 75 ins; 141 del; 49 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3135.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3135/head:pull/3135

PR: https://git.openjdk.java.net/jdk/pull/3135