fix bug #688643
Command-line option process separatelly from system varaibles.
For variable use_global_log_slow_control I do following on update:
1) if current value use_global_log_slow_control contain "long_query_time" - set "use_global_long_query_time" to "ON"m otherwise - to "OFF"
2) Check variable value - if equal "0", add single value to set - "none".
For variable use_global_long_query_time I do following on update:
If value setuped to "ON" - I add "long_query_time" to current value of use_global_log_slow_control, otherwise (use_global_long_query_time=OFF) - remove value "long_query_time" from use_global_log_slow_control.
Now I use this logic for get_options in mysqld.cc and variables in set_var.cc both.
Also fix code style