Fix iter.zip.
Fix iter.zip.

This doesn't appear to be called anywhere but is presumably available
for symmetry so the implementation roughly matches the slightly quirky
Ary#zip.  These might be better generalised at some point.

invl/dactyl,5digits/dactyl,Kjwon15/dactyl,Kjwon15/dactyl,nathyong/dactyl,airodactyl/dactyl,moonshadow/dactyl,nathyong/dactyl,madand/pentadactyl-pm,madand/pentadactyl-pm,5digits/dactyl,airodactyl/dactyl,madand/pentadactyl-pm,invl/dactyl,moonshadow/dactyl,airodactyl/dactyl,invl/dactyl,nathyong/dactyl,moonshadow/dactyl,airodactyl/dactyl,moonshadow/dactyl,invl/dactyl,nathyong/dactyl,airodactyl/dactyl,nathyong/dactyl,Kjwon15/dactyl,madand/pentadactyl-pm,madand/pentadactyl-pm,airodactyl/dactyl,5digits/dactyl,madand/pentadactyl-pm,5digits/dactyl,5digits/dactyl,moonshadow/dactyl,moonshadow/dactyl,invl/dactyl,nathyong/dactyl,Kjwon15/dactyl,5digits/dactyl,Kjwon15/dactyl,Kjwon15/dactyl,invl/dactyl