A plain click on an item in the library panel selected the item but did
not record it as the anchor that a Shift-click ranges from. A later
Shift-click then selected only the clicked item, or ranged from an
older anchor set by an earlier Cmd/Ctrl-click or folder click. This
applied to swatch libraries and graphic style libraries.
Every click on an item or folder now goes through click_selection, as
in the Swatches panel. A plain click still selects the item alone and
adds and applies it.