Remove alignment restriction on RawArrayView/Mut

[jturner314]

This makes .cast() safe without a check for alignment.

This might be a breaking change because we documented that RawArrayView/Mut had alignment requirements. I suppose it depends on how that statement could be interpreted. Someone could think that it would mean that, given any RawArrayView, it would be safe to call .deref_into_view() without ensuring that the pointer was aligned. IMO, though, since we didn't say exactly what the alignment restrictions were, no one should have made that assumption.

[bluss]

Thanks a lot. I patched it to use as for raw pointer casts, the cast method on raw pointers was a Rust 1.37 or 1.38 feature apparently (and it was a bit earlier on NonNull).

[bluss]

I don't see it as a breaking change, this refinement of detail seems reasonable.

[jturner314]

Okay, sounds good. Thanks for fixing up the PR for Rust 1.37.