Alternative version formally accepted into Boost.

svn path=/sandbox/boost/optional.hpp; revision=943
Added version by Fernando Cacciola (to be removed on release of next version of Boost).

svn path=/sandbox/boost/optional.hpp; revision=944
Added missing detail/workaround.hpp #include.

svn path=/sandbox/boost/optional.hpp; revision=951
Updated to match 1.30.0 release.

svn path=/sandbox/boost/optional.hpp; revision=1108