fix warning "type qualifiers ignored on function return type" for long long scalar types
fix warning "type qualifiers ignored on function return type" for long long scalar types

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