[PATCH] Fix TUpDown widgets with swapArrows=true

[Thomas Glamsch]

TUpDown widgets with swapArrows=true could be set to values below their minimum when using mouse clicks.
This mostly concerned numeric values such as audio volume and rendering quality in the settings menu.
While this patch fixes the bug, I would suggest redesigning that widget class completely since it is pretty convoluted right now.

[Marko Lindqvist]

Thanks. Pushed.