Maligned causes incorrect deallocation

Summary

`maligned::align_first` manually allocates with an alignment larger than T, and then uses `Vec::from_raw_parts` on that allocation to get a `Vec<T>`. [`GlobalAlloc::dealloc`](https://doc.rust-lang.org/std/alloc/trait.GlobalAlloc.html#tymethod.dealloc) requires that the `layout` argument must be the same layout that was used to allocate that block of memory. When deallocating, `Box` and `Vec` may not respect the specified alignment and can cause undefined behavior.