mon/tripemon.in: Support the new-style bindings for Gtk and friends.

mon/tripemon.in: Support the new-style bindings for Gtk and friends.

This is a fair amount of tedious work, especially if we want to keep
compatibility with the old versions of things.

Highlights:

  * There are separate modules now for GLib and GObject, as in the
    underlying C libraries; the old Python bindings merged the two
    together.

  * Gtk enumerations and flags now live in their own classes, so we dig
    them out for compatibility.

  * Because the new bindings are dynamically generated from
    introspection data, they don't make allowances for (say) `raise'
    being a Python reserved word.

  * Some functions which used to have default arguments no longer do, so
    we have to call them the hard way.