Add dependency on conf-glade to gtktop.

Fixes errors for

* [gtk-top](https://github.com/ocaml/opam-bulk-logs/blob/master/20140606/roo/4.01.0/raw/gtktop#L1784-L1813)
* [ocamltop-gtk](https://github.com/ocaml/opam-bulk-logs/blob/master/20140606/roo/4.01.0/raw/ocamltop-gtk#L1787-L1816)