Failing test case for sorting NaN values.
Better test case to demonstrate NaN sorting issue.

This also applies to undefined values, which is where I first noticed it
(a dataset where around half the values were undefined). This quicksort
implementation is unstable, so my previous attempt at an appropriate
test case didn't correctly detect the issue.
Fix sorting of undefined and NaN.

Unfortunately, this slows things down a bit due to the additional pass,
but perhaps it can be optimised later.
Simplify.
Fix insertion sort for NaN values.
added support for union of multiple filters
fixed bug - needed to expand hi0/lo0 range to include all ranges
Adding patch for filter multiple values
Merging sort-nan branch
testing