#1007 Long callback: One click -> Two steps

[Don Porter]

Evaluate the demo script in wish.

Click once in the trough of the scale. Do
not hold the button down.

Watch the scale advance two steps.

This problem can be worked around by configuring
the -repeatdelay of the scale, but that's not
obvious from the documentation pages.

Documentation improvements are probably sufficient
to close this bug.

[Don Porter]

Demo script