RFR: 8229517: Support for optional asynchronous/buffered logging [v3]

[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:

 - fix runtime/logging/RedefineClasses.java crashed with -XX:+AsyncLogging
   
   nmethod::print(outputStream* st) should not obtain tty_lock by assuming
   st is defaultStream. It could be logStream as well.
   
   Currently, AyncLogFlusher::_lock has the same rank of tty_lock.
   https://issues.amazon.com/issues/JVM-563
 - 8229517: Support for optional asynchronous/buffered logging
   
   Move LogAsyncFlusher from WatcherThread to a standalone NonJavaThread
   https://issues.amazon.com/issues/JVM-565
 - 8229517: Support for optional asynchronous/buffered logging
   
   re-introduce the global option AsyncLogging.

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/3135/files
  - new: https://git.openjdk.java.net/jdk/pull/3135/files/bcefbecb..81b2a0cb

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=3135&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=3135&range=01-02

  Stats: 113 lines in 9 files changed: 74 ins; 22 del; 17 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