Rename Invert to Flip - Issue #10632

[mankyKitty]

Renamed the invert() function in iter.rs to flip(), from #10632

Also renamed the Invert<T> type to Flip<T>.

Some related code comments changed. Documentation that I could find has
been updated, and all the instances I could locate where the
function/type were called have been updated as well.

This is my first contribution to Rust! Apologies in advance if I've snarfed the
PR process, I'm not used to rebase.

I initially had issues with the codegen section of the tests failing, however
the make check process is not reporting any failures at this time. I think
that was a local env issue more than me facerolling my changes. :)

[alexcrichton]

We should discuss this before merging as it doesn't look like there was consensus on the issue of what course of action to take.

[thestinger]

I'm okay with renaming this. I don't really care much either way but I think flip is more discoverable. I had to think of a name that wasn't reverse as it was already used, and invert is what I came up with.

[mankyKitty]

I just commented on the issue, I was thinking maybe it should be flip_iter or flip_iter_direction since it's the direction of the iterator that is being flipped, not the collection itself.. If I've understood things correctly.

That is if people aren't happy with flip(). Obviously I am already, but that's hardly the point. :P haha

[liigo]

+1 for Rev<T>

[alexcrichton]

I, too, think that Rev and rev would be suitable names for the type and method.

It doesn't sound like there's much opposition to these names, so would you mind rebasing with the new names?

[mankyKitty]

Not a problem. :)