Ensures that there are at least extra free stack slots in the stack. It returns false if it cannot grow the stack to that size. This function never shrinks the stack; if the stack is already larger than the new size, it is left unchanged.
[Visual Basic] Public Shared Function lua_checkstack( _ ByVal L As IntPtr, _ ByVal sz As Integer _ ) As Integer
[C#] public static int lua_checkstack( IntPtrL, intsz );