title: std::vector::erase exception safety
body: <p>I have read that std::vector erase method use move operations only if type is known to not emit exceptions due to strong exception safety. Other comments are that erase method guarantee basic or no throw exception safety depending on that if element constructor throws or not. I wasn't able to clarify that in my C++11 draft. I did test and it shows basic exception safety guarantee, it also used move constructor which was not marked as noexcept. Did I overlook something ? What is right ?  </p>