Message 384675 - Python tracker

Ok, it's now fixed.

To make sure that a heap type can be deleted, it must by a GC type, has a traverse function, and it must track its instances. We should take this in account when we convert static types to heap types. In practice, deleting a type is mostly an issue when we check for reference leak and an instance is kept alive until the last GC collection, at the end of Py_EndInterpreter().