EscoFileChooserThingie

I just got the EscoFileChooserButton (mostly) working. Here’s a screenshot of the widget in open and save modes (Update: the “Save” entry does autocomplete using GtkFileChooserEntry):

The remaining things to do are:

1. Make the button text not expand the size of the button to huge widths for long paths.
2. Make DnD (& Copy/Paste?) of file/folders Just Work.
3. Re-organize to GTK+-style prototypes & function order.
4. Convert to a patch to GTK+.
5. ???
6. Profit!