This patch makes the handling of constructor arguments consistent among
the Volatile_object and Lazy_volatile_object classes. Arguments are
always forwarded. Otherwise, passing a reference as argument would result
in an unwanted copy of the passed object.
This patch changes the top-level directory layout as a preparatory
step for improving the tools for managing 3rd-party source codes.
The rationale is described in the issue referenced below.
Issue #1082