Fix leaking engine objects on event loop exit.
Fix leaking engine objects on event loop exit.

Ignore-this: 7bbbb9459cb8371ce67535fc95673d40

darcs-hash:20120528215829-4d2ae-eefbede83ab7d91416f7b9af464fc559d45a75cd

johntyree/HsQML,johntyree/HsQML