add pop!(::Dict) to return a key=>value pair

[rfourquet]

I didn't find a discussion on this method, so I guess it's simply an omission. I propose it because I needed it.

[ararslan]

Since Dicts aren't ordered, this can return any pair? Seems kinda weird, IMO, since pop! to me typically implies removal from a well-defined position. Out of curiosity, what was your use case for this?

[iamed2]

For comparison, Python has dict.popitem() and dict.pop(key[, default])

[rfourquet]

This is no more weird than pop(::Set) returning any of its elements - and is what happens with normal iteration, where all the elements are visited in a non-specified order. This is useful for example if I want to iterate over all elements of a Set/Dict which can be modified, i.e. new elements are added from within the loop (I use the dict as a stack).

[ararslan]

Interesting, I didn't realize we supported pop!(::Set) either. I guess this is fine then, especially if it has precedent in other languages.

[StefanKarpinski]

LGTM