This problems was found while working on
Steps to reproduce:
1. In Moodle 1.9, create a course with a quiz.
2. As admin, go into the question bank for the quiz, and create a question in the 'Default for system' part of the question bank. Include some images in the question, but embedded in the question text, and also using the 'image' field.
3. Add the question to the quiz.
4. Backup the course.
5. Restore the course into Moodle 2.x.
6. Verify that the images in the question are now stored using the Moodle file API, and that they have not been lost.