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/test/unit/a0.c

@@ -0,0 +1,19 @@
+#include "test/jemalloc_test.h"
+
+TEST_BEGIN(test_a0)
+{
+	void *p;
+
+	p = a0malloc(1);
+	assert_ptr_not_null(p, "Unexpected a0malloc() error");
+	a0dalloc(p);
+}
+TEST_END
+
+int
+main(void)
+{
+
+	return (test_no_malloc_init(
+	    test_a0));
+}