Added mem::safe_recursive_clone, and while it works for regex, it's actually slower then remaking it. Hmmmm, maybe because some of the stdlib is inefficent

tests/test_rec_closure.expected_results

@@ -0,0 +1,5 @@
+thingy: 4
+thingy: 3
+thingy: 2
+thingy: 1
+thingy: 0