Added initial implementation of move_if_noexcept

This is an initial implementation of [move_if_noexcept](http://www.cplusplus.com/reference/utility/move_if_noexcept/) .

Checked it with tests of Boost.CircularBuffer - works OK on GCC in C++11 and C++03 modes. I'll add some tests directly to the Boost.Move a little bit later.

Questions:
* Is it OK to include <boost/move/traits.hpp> in <boost/move/utility.hpp> ?
* I'm not sure about BOOST_MOVE_OLD_RVALUE_REF_BINDING_RULES part. Could you please take a closer look at it?