Add some cross-references to the docs.  Simplify the python code equivalent for izip().  Supply an optional argument for the nth() recipe.

for issue5293.

The file was resized to wrong size.

Add versionadded tags.

and cleanups in Objects/longobject.c.  The most significant change is that
longs now use less memory:  average savings are 2 bytes per long on 32-bit
systems and 6 bytes per long on 64-bit systems.  (This memory saving already
exists in py3k.)