More Operations on Lazy Lists

We formalize some operations and reasoning infrastructure on lazy (coinductive) lists. The operations include: building a lazy list from a function on naturals and an extended natural indicating the intended domain, take-until and drop-until (which are variations of take-while and drop-while), splitting a lazy list into a lazy list of lists with cut points being those elements that satisfy a predicate, and filtermap. The reasoning infrastructure includes: a variation of the corecursion combinator, multi-step (list-based) coinduction for lazy-list equality, and a criterion for the filtermapped equality of two lazy lists.