
Switching to Python3 seems to require more Gtk3 changes.
(Maybe just that non-keyword arguments are deprecated.)

Gtk.Button(lbl) ==> Gtk.Button(label=lbl)
Gtk.Window(wtype) ==> Gtk.Window(type=wtype)
Gtk.ScrolledWindow(hadj, vadj) ==>
    Gtk.ScrolledWindow(hadjustment=hadj, vadjustment=vadj)


Get rid of the std::string typemaps?  Just the "in" typemaps?  Tell
swig that the args are char* or const char* and let it handle the
string conversion.
