Fix some reference leaks.
Use QMetaType::Type values instead of obsolete QVariant::Type.
Use PyGILState_{Ensure,Release} to play well with recursive GIL acquisitions.
Wrap generic PyObjects in an opaque value that can be passed to/from QML safely.
Merge pull request #25 from fkrull/refleaks

Fix some reference leaks.
Removed QMutex in QPythonPriv.
Calling methods on Python objects.
Access attributes of Python objects.
OpenGL rendering in python.
Removed some unused private members.
Print exceptions in renderer methods.
Recreate renderer when callbacks have been redefined.
Added null-checks for callbacks.
PyGLArea: Pass renderer object instead of function names.
Update PyGLArea when properties have changed.
Improved PyGLArea documentation, added example.
Removed property PyGLArea.t (leftover from Qt tutorial).
Only disable automatic clearing when rendering before QML.
Fixed reference leaks in callMethod_sync() and getattr().
OpenGL rendering to FBO.