This is useful for creating byte buffers of actually-different-things.
Copied the argument order from `Allocator.alignedAlloc`

I noted that `ArrayListAligned` is going out of it's way to not set the
alignment at comptime when it is not specified. However, I was not able
to do that the same way here, and good people on IRC, @ifreund in
particular (thanks!) assured me that

    [N]T align(@alignOf(T))

is equivalent to

    [N]T