The documentation on AbstractType says subclasses must have a BaseType typedef. However, very few types actually had it, and nothing uses it anymore (apparently only the oldcpp code used it in the past).
So I'm removing the remaining BaseType typedefs, and adjusting the doxygen comment that says you need it.
If approved, I'll send patches for other repos too (kdevelop has 1 remaining BaseType and kdev-python has 3).