> val _ aNumber - self first / self increment.
>  ^ ( val - val rounded ) abs < 1e-10

This takes no account of the bounds AFAICS*; it needs fuzzy checks for upper
and lower bounds, which previous versions have done.  However, it deals
neatly with the scaling problem.

* Try (1500 to: 1700 by: 0.01) valuesInclude: 0.  I get val as (0 - 1500) /
0.01 = -150,000.  val - val rounded will be close to 0, and the test will
return true.

		- Peter