* Curves: Cmd/Ctrl-click on the image adds a point at the pixel's tone (part of #7325)
With Image > Adjustments > Curves open, a Cmd-click (Ctrl-click off the Mac) on
the image adds a point to the channel shown in the dialog, at the pixel's tone
and at the curve's current output there; Shift adds one point on each of Red,
Green and Blue. Only the press adds, an armed eyedropper still wins, and the
control channel's ui.pointer does the same with command: true.
* Curves: Cmd/Ctrl-click adds the point with the Hand tool too; Space and middle button still pan
The Hand tool took the Cmd-click press for a pan, so no point was added; the
press now counts before the Hand. On the control channel, ui.pointer with
space or the middle button pans as the mouse does instead of adding a point.
* Curves: the Cmd/Ctrl-click point's comment says where the curve can still change
