[boost] Illegal specialisation in boost/mpl/math/is_even.hpp

boost/mpl/math/is_even.hpp contains a specialisation of a template in a different namespace to the original declaration. This causes an error with GCC 3.4 (and should fail with Comeau in strict mode). I believe the attached patch should fix it, but haven't yet been able to run the tests again to find out. jon -- "We are the Music Makers, and we are the Dreamers of Dreams." - Arthur William Edgar O'Shaughnessy