Start transition to libxml++ for saving level objects
Make balls save with new XML lib
Make basebox and bonubox save with the new XML lib
Make spinbox save with the new XML lib
Make textbox save with the new XML lib
For DEBUGING, only dump to standard output on level saving.
Add missing cSprite serialization.

Actually, I overlooked that cSprite did also have a Do_XML_Saving()
method itself.
Make goldpiece save with the new XML lib
Make level exits save using the new XML lib
Make levelexit save with the new XML lib