[boost] irritation in ublas/lu.hpp

Real quick: numeric/ublas/lu.hpp will not compile on its own, it requires at least operation.hpp for the symbol axpy_prod<>. In the absence of examples, one of my users included matrix.hpp , vector.hpp, and lu.hpp intending to do some lu-decompositions, and was stymied when the headers wouldn't compile. As lu.hpp is not included from anywhere else, it appears that it is *not* a header that is designed not to be used directly... I asked on #boost, can't come up with an explanation, therefore submit as bug^-2 -t