Jemalloc updated to 4.4.0.

The original jemalloc source tree was modified to:

1. Remove the configure error that prevents nested builds.
2. Insert the Redis private Jemalloc API in order to allow the
Redis fragmentation function to work.

deps/jemalloc/msvc/projects/vc2015/test_threads/test_threads.h

@@ -0,0 +1,3 @@
+#pragma once
+
+int test_threads();