re PR libstdc++/58357 (In C++11 std::rotate(first, middle, last) now should return a forward iterator to  first + (last - middle).)

	PR libstdc++/58357
	* include/bits/algorithmfwd.h (rotate): Move to inline namespace _V2.
	* include/bits/stl_algo.h (__rotate, rotate): Likewise.

From-SVN: r220823