Maybe all derived classes should get their own GType automatically.

Submitted by Murray Cumming @murrayc

Link to original bug (#546220)

Description

In some cases we need to call Glib::ObjectBase("somename") to create a new GType for the derived C++ class, sometimes even just using RTTI to get a name. For instance, for derived CellRenderers or TreeModels, though I need to discover why that's really necessary.

If it's possible somehow, maybe we should just do this automatically for all derived classes.

Version: 2.17.x