CLAMP checks both if n_taps is '< 0' and '> max_taps'. n_taps will never be a
negative number because it is an unsigned integer. Removing that check and only
making sure it isn't set bigger than max.
CID 1256558
when using variable taps and when we are limiting the number of taps,
recalculate the lanczos parameters to match the clamped value.
Set the max number of taps to 128
Add an option to limit the number of taps to use in automatic mode. The
problem is that for lanczos, we might use more taps than what we can
handle with the current precision.
Rework the other options a little to make it nicer to set defaults.
