lua lock?

[Carl Michaels <carlm@...>]

Hi,

I've been looking through the code and see various lua_lock and 
lua_unlock. I looked up these and found that both were just the following 
macro:

#define lua_lock(L)	((void) 0)

How exactly does this lock work? Also why does it need a #ifndef in front 
of it?

Thanks,
Carl