any_cast doesn't work with rvalue reference targets and cannot
	move with a value target.
	* include/experimental/any (any(_ValueType&&)): Constrain and
	add an overload that doesn't forward.
	(any_cast(any&&)): Constrain and add an overload that moves.
	* testsuite/experimental/any/misc/any_cast.cc: Add tests for
	the functionality added by LWG 2509.

From-SVN: r238022