option is_some() should not require a copyable value

[nikomatsakis]

But it does now. Same with is_none(), iter(), and map() I believe. And possibly others.

[eholk]

Does this go for vectors too? I think I've been having to add copy bounds, but if we're clever we should be able to rewrite them without needing copy.

[nikomatsakis]

It often applies to vectors, yes.