Have use_allocate_node also check alignment

[jodyhagins]

For the segregator, it checks the size of the allocation. However, some allocators (I'm looking at you, memory_pool_collection_allocator) throw if the requested alignment is too big. However, the segregator could have a fallback allocator that supports the larger alignment.

If we just made a hard change, this could break existing code. Thus, another parameter can be passed to the threshold constructor that can enable alignment checking. It is a strong type so there should be no inconvenient implicit conversions and in order to get the new behavior, it will have to be explicitly requested.