win32: Fix DnD when drag icon is below the pointer
win32: Fix DnD when drag icon is below the pointer

By reverting gdk_drag_find_window_for_screen logic to what it was
before eb21a7df290936223f6a80cef36b52a8c68a1d22.
The old logic knew how to ignore drag_window when searching
for dest_window, but that code was removed (I guess by accident).

https://bugzilla.gnome.org/show_bug.cgi?id=616544

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