Adjust the drag destination row when it is above the currently highlighted row
Adjust the drag destination row when it is above the currently highlighted row

This makes the feedback accurate and without hysteresis.  Haven't I written this code ten times before?

Signed-off-by: Federico Mena Quintero <4999915a961edfd7686112c2935288e1266eae14@gnome.org>

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