Added tests for bug #716 - QPersistentModelIndex isn't convertible to QModelIndex

The main test (exactly the same as reported) was added to QtGui tests,
but also extended QAbstractItemModel test with a case that is the
essence of the problem.

http://bugs.pyside.org/show_bug.cgi?id=716

Reviewed by Hugo Parente <hugo.lima@openbossa.org>
Reviewed by Luciano Wolf <luciano.wolf@openbossa.org>

tests/QtCore/qabstractitemmodel_test.py

@@ -16,6 +16,13 @@ class TestQModelIndexInternalPointer(unittest.TestCase):
         foo = Foo()
         idx = m.createIndex(0,0, foo)
 
+    def testPassQPersistentModelIndexAsQModelIndex(self):
+        # Related to bug #716
+        m = MyModel()
+        idx = QPersistentModelIndex()
+        m.span(idx)
+
+
 if __name__ == '__main__':
     unittest.main()