[boost] Porting boost::lexical_cast tests to boost::convert

Hi, Since boost::convert is promoting itself as an alternative to boost::lexical_cast I decided to port the boost::lexical_cast test suite (which can be found in BOOST_ROOT/libs/conversion/lexical_cast_test.cpp) to boost::convert. I've simply replaced lexical_cast<T>(U) with convert<T>::from(U) and bad_lexical_cast with std::invalid_argument, whether this is a valid approach I'm not sure. To actually get the test suite to compile for boost::convert I had to comment out a lot of them and even then there are quite a few failures. This needs to be looked at (I've attached the code), what are actual boost::convert failures (both at compile- and runtime) and what is caused by my porting? Regards, Jeroen