Fix refcount problems seen when re-initializing Python after finalizing
Fix refcount problems seen when re-initializing Python after finalizing

A sequence of calls like the following would crash in Python when reinitializing
the interpreter the second time:

    PythonQt::init(0);
    ...
    Py_Finalize();

    PythonQt::init(0);
    ...
    Py_Finalize();

msmolens/PythonQt,msmolens/PythonQt,msmolens/PythonQt,rkhlebnikov/PythonQt,rkhlebnikov/PythonQt,msmolens/PythonQt,rkhlebnikov/PythonQt,rkhlebnikov/PythonQt