> I think patch for 3.3 should mention only shlex.quote.

+1

I'm not sure what's the best thing to do about pipes.quote.  Pointing to an undocumented function that is available in 3.3 in a different module doesn't sound like a really good idea.
Maybe we could document pipes.quote as an internal/deprecated function so that people that follow the link from the subprocess docs will be aware that the function is available under a different name in 3.3+.
Otherwise we could just document shlex.quote() in 3.3+.