lua_*libopen() leaves a table on the stack

["Nick Davies" <goodbytes@...>]

I'm not sure if this is supposed to happen, but the behavior isn't
documented. So...

Using Lua 5.0-beta, when I call lua_mathlibopen(), or any other function
that opens a Lua library, after the function returns, a value of type table
is left on the Lua->C stack. I have a couple of questions regarding this...

1) Is this supposed to happen?
2) If so, why does it happen? What is the use of this table on the stack,
and am I supposed to do something with it?

Nick