Call user function in each main loop iteration

[Rodolfo Lima <rodolfo rodsoft org>]

Hi, I wonder if there's a way to set up a user-defined function to be
called in every loop iteration. For what I saw in glib/gtk+ code, there
isn't a way to do that, but then I may be wrong.

This would be used in wxWidgets' GTK port, where its Windows counterpart
enables us to manually run the main event loop, customizing it for doing
other processing duties.

Regards,
rod