fix bug 242: vectorization was wrongly enabled on MSVC 2005
fix bug 242: vectorization was wrongly enabled on MSVC 2005

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