fix a strict aliasing issue with gcc 4.3
fix a strict aliasing issue with gcc 4.3

madlib/eigen_backup,rotorliu/eigen,mjbshaw/Eigen,rotorliu/eigen,madlib/eigen_backup,rotorliu/eigen,mjbshaw/Eigen,madlib/eigen_backup,rotorliu/eigen,mjbshaw/Eigen,mjbshaw/Eigen,madlib/eigen_backup