zstandard: vendor python-zstandard 0.11 The upstream source distribution from PyPI was extracted. Unwanted files were removed. The clang-format ignore list was updated to reflect the new source of files. The project contains a vendored copy of zstandard 1.3.8. The old version was 1.3.6. This should result in some minor performance wins. test-check-py3-compat.t was updated to reflect now-passing tests on Python 3.8. Some HTTP tests were updated to reflect new zstd compression output. # no-check-commit because 3rd party code has different style guidelines Differential Revision: https://phab.mercurial-scm.org/D6199

--- a/contrib/python-zstandard/zstd/common/pool.c	Thu Apr 04 15:24:03 2019 -0700
+++ b/contrib/python-zstandard/zstd/common/pool.c	Thu Apr 04 17:34:43 2019 -0700
@@ -88,8 +88,8 @@
             ctx->numThreadsBusy++;
             ctx->queueEmpty = ctx->queueHead == ctx->queueTail;
             /* Unlock the mutex, signal a pusher, and run the job */
+            ZSTD_pthread_cond_signal(&ctx->queuePushCond);
             ZSTD_pthread_mutex_unlock(&ctx->queueMutex);
-            ZSTD_pthread_cond_signal(&ctx->queuePushCond);
 
             job.function(job.opaque);