Bug 607628 - DnD operation doesn't work when using offscreen
Bug 607628 - DnD operation doesn't work when using offscreen

Changed the way to find the drop widget from a top->bottom recursion
using GdkWindow positions to a liner bottom->top walk up the widget
hierarchy using _gtk_widget_find_at_coords() and
gtk_widget_translate_coordinates(), which both do the right things for
offscreen widgets.
(cherry picked from commit cb8c0763215bd18219c2d32b56e4bfe8a576f6b3)

ahodesuka/gtk,alexlarsson/gtk,ebassi/gtk,simokivimaki/gtk,ahodesuka/gtk,grubersjoe/adwaita,grubersjoe/adwaita,davidgumberg/gtk,jigpu/gtk,bratsche/gtk-,davidt/gtk,alexlarsson/gtk,simokivimaki/gtk,chergert/gtk,chergert/gtk,jadahl/gtk,simokivimaki/gtk,msteinert/gtk,davidgumberg/gtk,chergert/gtk,chergert/gtk,chergert/gtk,bratsche/gtk-,jigpu/gtk,Distrotech/gtk2,jessevdk/gtk,jessevdk/gtk,Lyude/gtk-,jadahl/gtk,ebassi/gtk,ebassi/gtk,chergert/gtk,ahodesuka/gtk,Distrotech/gtk2,chergert/gtk,ahodesuka/gtk,jadahl/gtk,Lyude/gtk-,alexlarsson/gtk,Sidnioulz/SandboxGtk,jessevdk/gtk,alexlarsson/gtk,davidt/gtk,simokivimaki/gtk,ahodesuka/gtk,Sidnioulz/SandboxGtk,jigpu/gtk,Adamovskiy/gtk,Adamovskiy/gtk,Sidnioulz/SandboxGtk,ebassi/gtk,jigpu/gtk,jigpu/gtk,davidt/gtk,grubersjoe/adwaita,msteinert/gtk,Adamovskiy/gtk,Adamovskiy/gtk,alexlarsson/gtk,davidgumberg/gtk,jessevdk/gtk,davidgumberg/gtk,ebassi/gtk,Lyude/gtk-,Adamovskiy/gtk,ahodesuka/gtk,jadahl/gtk,bratsche/gtk-,Lyude/gtk-,Distrotech/gtk2,jigpu/gtk,msteinert/gtk,msteinert/gtk,jadahl/gtk,grubersjoe/adwaita,simokivimaki/gtk,Adamovskiy/gtk,Lyude/gtk-,Adamovskiy/gtk,grubersjoe/adwaita,Sidnioulz/SandboxGtk,Adamovskiy/gtk,msteinert/gtk,grubersjoe/adwaita,davidgumberg/gtk,Distrotech/gtk2,alexlarsson/gtk,jigpu/gtk,Sidnioulz/SandboxGtk,grubersjoe/adwaita,bratsche/gtk-,msteinert/gtk,bratsche/gtk-,ahodesuka/gtk,jessevdk/gtk,ebassi/gtk,Distrotech/gtk2,jadahl/gtk,jessevdk/gtk,Distrotech/gtk2,jigpu/gtk,davidt/gtk,jessevdk/gtk,ahodesuka/gtk,davidt/gtk,Lyude/gtk-,davidt/gtk,davidgumberg/gtk,alexlarsson/gtk,grubersjoe/adwaita,bratsche/gtk-,Sidnioulz/SandboxGtk,chergert/gtk,jadahl/gtk,Lyude/gtk-,alexlarsson/gtk,Lyude/gtk-,davidgumberg/gtk,davidgumberg/gtk,simokivimaki/gtk,jadahl/gtk