query-editor: avoid double borders in Select Type dialog
path bar: Request enough natural width to fit all buttons

Otherwise, we are at the mercy of the container giving us
more space than we request, which does not always work.

https://bugzilla.gnome.org/show_bug.cgi?id=722542
toolbar: Port to GtkHeaderBar

https://bugzilla.gnome.org/show_bug.cgi?id=722542
Fix window dragging on the path bar

GtkWindow relies on button press, release and motion notify
events being propagated. Therefore, we need to select for
motion notify events to make window dragging work.

https://bugzilla.gnome.org/show_bug.cgi?id=722542
bookmark: fix runtime warning

We did not reset the timeout id to zero when the callback was reached,
causing the finalize code to try to remove an invalid source ID later.