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/fork.c

@@ -0,0 +1,64 @@
+#include "test/jemalloc_test.h"
+
+#ifndef _WIN32
+#include <sys/wait.h>
+#endif
+
+TEST_BEGIN(test_fork)
+{
+#ifndef _WIN32
+	void *p;
+	pid_t pid;
+
+	p = malloc(1);
+	assert_ptr_not_null(p, "Unexpected malloc() failure");
+
+	pid = fork();
+
+	free(p);
+
+	p = malloc(64);
+	assert_ptr_not_null(p, "Unexpected malloc() failure");
+	free(p);
+
+	if (pid == -1) {
+		/* Error. */
+		test_fail("Unexpected fork() failure");
+	} else if (pid == 0) {
+		/* Child. */
+		_exit(0);
+	} else {
+		int status;
+
+		/* Parent. */
+		while (true) {
+			if (waitpid(pid, &status, 0) == -1)
+				test_fail("Unexpected waitpid() failure");
+			if (WIFSIGNALED(status)) {
+				test_fail("Unexpected child termination due to "
+				    "signal %d", WTERMSIG(status));
+				break;
+			}
+			if (WIFEXITED(status)) {
+				if (WEXITSTATUS(status) != 0) {
+					test_fail(
+					    "Unexpected child exit value %d",
+					    WEXITSTATUS(status));
+				}
+				break;
+			}
+		}
+	}
+#else
+	test_skip("fork(2) is irrelevant to Windows");
+#endif
+}
+TEST_END
+
+int
+main(void)
+{
+
+	return (test(
+	    test_fork));
+}