We now specialize std::less<const std::type_info*> to use
std::type_info::before(), and on Windows and Mac that Just Works. It even
works on Linux when using gcc 4.4+: more recent implementations of gcc's
std::type_info::before() apparently do name()-string comparisons internally.
It doesn't work so well on Linux with gcc 4.1, though, and that's the compiler
we still use on our Linux build-farm machines. But rather than give up,
perform explicit name()-string comparison in that case.