optional parameters

RFC for optional parameters added to Rust functions
I don't argue that some of our stdlib functions could be better named, but finding better names is not impossible. I also don't argue that optional parameters will allow strictly nicer names some of the time; god knows I've wished for them before. But keep in mind that up till now our stance has been that being forced to name your functions explicitly has been considered a feature, and that the lack of overloading/optional parameters has been an explicit choice (though entirely subjective). To overcome this inertia, you'd be best served by showing before/after comparisons of how real-life stdlib functions would look (both in definition and in usage) if this change were accepted.