RFR: ClassicProblem_02_ProducerConsumerProblem - third try

[Michael Mirwaldt]

This sample implements some solutions from the wikipedia article about the producer-consumer-problem on https://en.wikipedia.org/wiki/Producer%E2%80%93consumer_problem .
It contains these solutions:
- _OneProducerOneConsumer_ with semaphores
- _FlawedTwoProducersOneConsumer_ with semaphores in which the producers sometimes use the same index for their items and overwrite each others item in the buffer
- _FixedTwoProducersOneConsumer_ with semaphores which uses an extra lock for the index so that the producers never use the same index for their items
- _Lock_ doesn't use any sempahores but a reentrant lock with two conditions. It supports many producers and many consumers
- _AtomicIntegers_ neither uses any semaphores but two atomic integers and supports one producer and one consumer.

I have decided not to implement the last solution with finite-range single writer registers in the wikipedia article. It looked far too complicated to me.

This is my third try to avoid squash commits.

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Commit messages:
 - created first draft of sample ClassicProblem_02_ProducerConsumerProblem

Changes: https://git.openjdk.java.net/jcstress/pull/104/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jcstress&pr=104&range=00
  Stats: 312 lines in 1 file changed: 312 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jcstress/pull/104.diff
  Fetch: git fetch https://git.openjdk.java.net/jcstress pull/104/head:pull/104

PR: https://git.openjdk.java.net/jcstress/pull/104