#153 Tk regressions

[Alan W. Irwin]

-dev tk, test_tk_plgrid, and likely every other way we use the plframe widget exhibits two regressions from previous behaviour. Any effort to use the zoom functionality ends with a black screen. This worked within the last year or so. Any effort to use the page/setup menu has no effect on the plot. It may be a stretch to call this one a regression since I think it has been a long time since this worked.