RUBY-172 fix for OrderedHash#clone

lib/bson/ordered_hash.rb

@@ -158,6 +158,9 @@ module BSON
         end
       end
 
+      def clone
+        Marshal::load(Marshal.dump(self))
+      end
     end
   end
 end

test/mongo_bson/ordered_hash_test.rb

@@ -187,4 +187,11 @@ class OrderedHashTest < Test::Unit::TestCase
     assert !new.keys.include?('z')
   end
 
+  def test_clone
+    copy = @oh.clone
+    assert copy.keys == @oh.keys
+
+    copy[:foo] = 1
+    assert copy.keys != @oh.keys
+  end
 end