Fix bug 466: race condition destected by helgrind in manage_caching_sizes. After all, the solution based on threadprivate is not that costly.
Fix bug 466: race condition destected by helgrind in manage_caching_sizes.
After all, the solution based on threadprivate is not that costly.

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