[gtkmm] Window Manager functionality via gtkmm

[Callum Prentice <lists callum com>]

one of the responsibilities of my app is to provide some simple window manager type
functionality so that when on startup and whenever windows are created or destroyed, my apps
sees the relevant events and does the right thing.

i figure that either i can get what i need via the regular gtkmm event structure or else find
some non-blocking alternative to Gtk::Main::run () and do the work myself in my main loop.

any suggestions ?