ImmutableVec::head vs Deque::front, etc

[brson]

Currently, Vec and slices don't implement Deque, but ImmutableVec defines head, and last, while Deque defines front and back. Both sets of functions have the same signature, but inconsistent naming. Nominating.

[brson]

Vec's also have mut_last and mut_head.

[brson]

Actually... they only have mut_last.

[pnkfelix]

I thought stability attributes should be used to deal with issues like this.

But still, seems reasonable to expect us to resolve this.

P-backcompat-libs, not 1.0 milestone.

[aturon]

Closing; conventions for these APIs have landed.