Allow some of the DUIM examples to build.

These were previously only set up for Windows. This lets them
build and run elsewhere (they still don't work with DUIM/Gtk+
correctly though).
[gtk] Export g-type-from-instance.
[duim,gtk] Fix gtk-tree-selection-get-selected-rows.
[gtk] Provide $GTK-STOCK-* constants.
[duim,gtk] Don't emit a signal when the scrollbar's adjustment changes

This doesn't seem to be needed anymore, see:
https://developer.gnome.org/gtk3/3.5/GtkAdjustment.html#GtkAdjustment-changed
[duim,gtk] Update grab-pointer and ungrab-pointer
[duim,gtk] Use cairo functions in establish-pen
Merge pull request #539 from fracek/duim-gtk-fixes-2

Duim gtk fixes 2
[duim,gkt] Always use a new cairo surface when drawing
Merge pull request #540 from fracek/duim-gtk-surface-crash-fix

[duim,gkt] Always use a new cairo surface when drawing
[duim,gtk] Cleanup whitespace.
[duim,gtk] No need to cache context.
[duim,gtk] Don't return drawable everywhere.

We don't use the drawable in the same way and don't need
it any longer.
[reversi] Rename to "Reversi" from "FD Reversi".
[duim,gtk] Don't need to reset color.

We destroy the context immediately, so no need to change the
color back.
[duim,gtk] gcontext is a CairoContext, not GdkGC.
[duim,gtk] Some initial color support.
[duim,gtk] Set a background color for clear-box.

I'm not sure if this is right, as it might be handled by
the caller.
[duim,gtk] Fix position/size for draw-ellipse.

This fixes drawing pieces in Reversi.
[duim,gtk] Use dylan's boolean type