* src/aboutdialog.cc: Include <libglademm/xml.h> instead of the
whole <libglademm.h> to save a tiny bit of compile time.
* src/controller.cc: ditto.

* src/filebuffer.cc: Same here, and also replace <gconfmm.h> by
<gconfmm/client.h>.
* src/filetree.cc: ditto
* src/mainwindow.cc: ditto
* src/prefdialog.cc: ditto.