Fix #4270

[simonster]

This also makes squeeze require a tuple and deprecates the version that takes an iterator. I doubt there are many instances where the
dimensions to be squeezed aren't constant.

[JeffBezanson]

It's a bit unsatisfying to need a staged function for something so simple. This function has always seemed marginal anyway. Do you find squeeze useful?
It'd be better if we can find a static arithmetic hack (e.g. https://gist.github.com/JeffBezanson/10612461) for this instead.

[simonster]

Unfortunately my life is full of 4, 5, and 6 dimensional arrays. I often use squeeze because I've done something like Y = std(sum(X, 4), 1) and I need to get rid of the extra dimensions so that I can pass Y to imshow or some other plotting command.

I think we can get type inference without a staged function if we annotate the tuple passed to reshape as ::typeof(_sub(size(X), dims)). I'm not sure we could avoid heap-allocating tuples in a loop without a staged function, but maybe that doesn't matter.

[simonster]

Here's the variant without a stagedfunction that uses _sub. (Not sure if we want to put static arithmetic in a module or if I'm okay copy/pasting that piece here.) It think it would be possible to avoid those heap-allocated tuples using recursion, but this is easier to read and if you're using squeeze in a tight loop you're probably doing something wrong.

[JeffBezanson]

These are actually already defined elsewhere in Base.

[JeffBezanson]

This is nicer; I'm fine with this version.