Links from the gtk reference manual to the gdk manual point to
library.gnome.org, where I hoped they would be to the local copy of the
gdk manual included in the package.

For example in GtkWidget.html the GdkRectangle under gtk_widget_draw
links to

http://library.gnome.org/devel/gdk/unstable/gdk-Points-Rectangles-and-Regions.html#GdkRectangle

where I think it could be

    ../gdk/gdk-Points-Rectangles-and-Regions.html#GdkRectangle