Closes the last clojure.core.cache gaps (now 1314/0/0, including the 1000-thread
cache-stampede):
- java.lang.Thread over Chez fork-thread (shared heap): (Thread. thunk) + start/
join/run/isAlive, on a "user-thread" tag distinct from Thread/currentThread's
interrupt shim. java.util.concurrent.CountDownLatch (count/mutex/condition).
- java.util.concurrent.ConcurrentHashMap = the mutable HashMap shim; get / count /
contains? read it (clojure.core), which SoftCache uses on its backing map.
- java.lang.ref.SoftReference / ReferenceQueue: no JVM GC reference semantics, so
the referent is held strongly (a SoftCache is unbounded rather than GC-evicting),
but enqueue / poll work so clear-soft-cache! drains the queue.
JVM-certified corpus rows. make test + shakesmoke green.
9312ad0937