...by moving common code into the Private ctor,
and catering for C++11 move semantics a bit.
Saves ~1.5KiB in text size on Linux GCC 4.9 C++11 release
builds.
Change-Id: I52ed7e47f76b69500a871844c0920e27fe51a127
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>