Added option to disable multi-threaded flush with innodb_use_mtflush = 0
option, by default multi-threaded flush is used.
Updated innochecksum tool, still it does not support new checksums.
execution and global memory heap on shutdown.
Added a funcition to get work items from queue without waiting and
additional info when there is no work to do for a extended periods.
waiting for a job. They should sleep and let other threads to their work. At
shutdown, we know that we put "work" and that is handled as soon as possible.
Fixed issue on multi-threaded flush at shutdown.
Removed unnecessary startup option innodb_compress_pages.
Added a new startup option innodb_mtflush_threads, default 8.