[LUA 5.1] collectgarbage

This function is a generic interface to the garbage collector.
It performs different functions according to its first argument, opt:

• "stop":
  stops the garbage collector.
  
• "restart":
  restarts the garbage collector.
  
• "collect":
  performs a full garbage-collection cycle.
  
• "count":
  returns the total memory in use by Lua (in Kbytes).
  
• "step":
  performs a garbage-collection step.
  The step "size" is controlled by arg
  (larger values mean more steps) in a non-specified way.
  If you want to control the step size
  you must experimentally tune the value of arg.
  Returns true if the step finished a collection cycle.
  
• "setpause":
  sets arg/100 as the new value for the pause of
  the collector.
  
• "setstepmul":
  sets arg/100 as the new value for the step multiplier of
  the collector.