mx NumericStepper does not respect decimal stepSize

I may get to this, but don't consider it urgent (relative to other things I am doing at the moment) just entering it as an issue for now. If anyone else wants to tackle it... go for it.

Test case:

The above increments in single units only, not 0.5 steps as it does in Flex. it also fails to decrement (probably rounding up each time, I suspect, which is why increment works by decrement fails)

Reproduce the issue with the mx:NumericStepper example using minimum="5", maximum="10", and stepSize="0.5". Start at the NumericStepper entry point and trace how decimal step values are handled; done means increments and decrements both follow 0.5 steps within the configured bounds.

Written by the indexing model from the issue text.