Revert "Revert "[GType] Use attribute before searching for GType property.""
Revert "Revert "[GType] Use attribute before searching for GType property.""

This reverts commit 8de5eff296acec2643538eac60520acf5c015ce2.

Now GdkWindow behaves properly as the gtype has been set.

sillsdev/gtk-sharp,sillsdev/gtk-sharp,sillsdev/gtk-sharp,sillsdev/gtk-sharp,sillsdev/gtk-sharp