Defined only if ParentAllocator.alignedAllocate exists. Expansion
occurs in place under the conditions required by expand. Shrinking
occurs in place if goodAllocSize(b.length) == goodAllocSize(s).
structQuantizer(ParentAllocator, alias roundingFunction)
Defined only if ParentAllocator.alignedAllocate exists. Expansion occurs in place under the conditions required by expand. Shrinking occurs in place if goodAllocSize(b.length) == goodAllocSize(s).