RFR: 8268638: semaphores of AsyncLogWriter may be broken when JVM is exiting. [v3]

[Xin Liu]

> All 3 semaphores used by AsyncLogWriter are static member data. CRT(`libsystem_c.dylib __cxa_finalize_ranges`) deletes them on MacOS. Currently, AsyncLog Thread doesn't exit at all. As a result, semaphore_wait/signal
> returns with KERN_INVALID_NAME(15) After those semaphore are destroyed. 
> 
> This patch change those to regular data members. This prevents from deleting.
> This patch also provides a general RAII class AsyncLogLocker which is analogous MutexLocker.

Xin Liu has updated the pull request incrementally with one additional commit since the last revision:

  Change AsyncLogLocker to SemaphoreLock.
  
  Per reviewer's feedback, Semaphore declares SemaphoreLocker as a friend.
  now SemaphoreLocker is a general RAII class.

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/4479/files
  - new: https://git.openjdk.java.net/jdk/pull/4479/files/b7f853de..63e1fddf

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=4479&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=4479&range=01-02

  Stats: 29 lines in 2 files changed: 18 ins; 4 del; 7 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4479.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4479/head:pull/4479

PR: https://git.openjdk.java.net/jdk/pull/4479