refactor: drop Boost.Move dependency

Implement constexpr definitions of forward and move to replace usage
of boost::move and boost::forward from the Boost.Move library.

Alter tests to use std::move instead of boost::move.

Remove the dependency on Boost.Move from build.jam

include/boost/optional/detail/optional_swap.hpp

@@ -54,7 +54,7 @@ struct swap_selector<true>
 #endif
 
 #ifndef BOOST_OPTIONAL_DETAIL_NO_RVALUE_REFERENCES
-# define BOOST_OPTIONAL_DETAIL_MOVE(EXPR_) boost::move(EXPR_)
+# define BOOST_OPTIONAL_DETAIL_MOVE(EXPR_) optional_detail::move(EXPR_)
 #else
 # define BOOST_OPTIONAL_DETAIL_MOVE(EXPR_) EXPR_
 #endif