Blender Git Loki

Fix: Don't ignore duplicate channels when doing border/circle/lasso select

While it is necessary to ignore duplicates when doing Deselect/Column Select
(where double-updates may result in nothing being selected), for borderselect,
not including the duplicates meant that sometimes, nothing would happen
if you were trying to borderselect keyframes originating from hidden channels.

This was first noticed in the greasepencil-object branch, but affects all
animation channel types.