Add (*gtk.Window).Close wrapper.
Add (*gtk.Window).Close wrapper.

This is the first GTK 3.10 specific function added to the gtk package.
As a build targeting GTK 3.10 is assumed, gotk3 needs to be built
using the build tag 'gtk_3_8' if using the older GTK 3.8.

Francesco149/gotk3,pekim/gotk3,visionect/gotk3,conformal/gotk3,visionect/gotk3,andre-hub/gotk3,pekim/gotk3,andre-hub/gotk3,Francesco149/gotk3,yamnikov-oleg/gotk3,pekim/gotk3,yamnikov-oleg/gotk3,LittleBuster/gotk3,gotk3/gotk3,yamnikov-oleg/gotk3,conformal/gotk3,andre-hub/gotk3,gotk3/gotk3,LittleBuster/gotk3