hashmap each should be pure

[jesse99]

I have an impl of BaseIter which needs to call each on a hashmap, but I can't because the hashmap's each is not pure.

Not sure how to work around this other than not using BaseIter which isn't very cool.

[jesse99]

Work around is to use an unchecked block.

[jesse99]

hashmap.size and probably others should also be pure.

[graydon]

Niko has some thoughts on whether or not to do this, and how, I believe; purity of iteration over containers is something at least I know he's done some design work on. I was going to suggest his newer core::send_map (which will likely take the place of std::map) but it seems iteration is impure there too.

[jesse99]

It's pure in master now.