Method that may be called to indicate that specified names
(only local parts retained currently: this may be changed in
future) should be considered "auto-wrapping", meaning that
they will be doubled to contain two opening elements, two
matching closing elements. This is needed for supporting
handling of so-called "unwrapped" array types, something
XML mappings like JAXB often use.
NOTE: this method is considered part of internal implementation
interface, and it is NOT guaranteed to remain unchanged
between minor versions (it is however expected not to change in
patch versions). So if you have to use it, be prepared for
possible additional work.