Step arg without a start arg was ignored.

Issue 5176: special-case string formatting in BINARY_MODULO implementation. This shows a modest (1-3%) speed-up in templating systems, for example.

Issue #5247: Improve error message when unknown format codes are used when using str.format() with str, unicode, long, int, and float arguments.

documentation.

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

for issue5293.