Heads-up: new parallel I/O manager merged

Hi, I've merged the new parallel I/O manager that Andreas Voellmy and Kazu Yamamoto have been working on. The new parallel I/O manager scales much better than the current one*: the number of requests per second scales almost linearly up to 32 cores I believe. Perhaps Andreas could post the numbers. If you see any bugs that you think are related to the new I/O manager, please let Andreas and Kazu know. * The current one (which replaced an even earlier one) scaled well in the number of open file descriptors and performed better than the I/O manager it replaced, but it didn't scale well to multiple cores. Cheers, Johan