The problem with existing static variables are that they are not properly cleared. When the Python interpreter is finalized and reinitialized they can contain invalid references. This patch fixes this issue.

> * It requires to write "var.obj" instead of just "var" to access the Python object

You can use a dynamic array of PyObject** instead of a linked list for collecting references to "static variables" or use gc_next/gc_refs for managing a linked list.