Add iterators, fix some bugs, add fold.

New iterators: Repeat, Count
Fix: SliceIter, Range.

First is fold, because it's a function. Map will have to either
allocate memory or be a type. Maybe I'll do both.
6ec6ef39ee64 — Nathan Michaels 10 months ago
Cartesian Product of arbitrary iterators.
b54e77d9bd78 — Nathan Michaels 10 months ago
Something iterating