Using 'return List<T>(std::move(dynList))' for transfer of content
(with implicit shrinking) into a plain List, and leave copy elision
to do the rest. The implicit transfer (move construct List from
DynamicList) will normally invoke resize (new/delete and moving
elements).
With 'return dynList.shrink()', it will first invoke an internal
resize (new/delete and moving elements), followed by a copy
construct as a plain list.
STYLE: avoid implicit cast to 'const List&' in constructors
7f062a8f5e