o.c.pvnames.ui: Check for disposed widget (PV names no longer needed)
swt.xygraph: Continue Autoscale regardless of Zoom buttons.

The idea to ignore autoscale whenever one of the Zoom buttons is active
seemed good, but doesn't work:
User may have selected HORIZONTAL_ZOOM to configure a time range,
but still expects the vertical value axes to auto-zoom.
Or user selected a VERTICAL_ZOOM to adjust _one_ axis,
but still expects _other_ vertical axes to auto-zoom
-> Since the zoom type is not specific to a certain axis,
   it is impossible to determine if maybe _this_ axis
   should suspend auto-zoom.
   -> Just to the auto-zoom, don't second-guess.