Optimize the memory benchmark:
- get rid of the global mutex to calculate statistics
- remove if() and switch() branches on critical code paths
- align memory blocks to OS page size
- use native machine word size instead of 'int'
Now if the help command is specified for a script, sysbench first check
if the script impelements a custom help command, and calls it. If no
custom command is defined, it checks whether the script declares any
command line options, in which case it prints their description. If
neither the help() function nor an option declaration is available,
sysbench prints an error message.
