ntdll: Add a stub implementation for RtlDllShutdownInProgress.

[Robert Shearman]

Mike McCormack wrote:
>
> Robert Shearman wrote:
>>> +NTSTATUS WINAPI RtlDllShutdownInProgress(void)
>
>> For undocumented functions like this, you should add a test case.
>
> That's unreasonable.  A stub isn't meant to work correctly, just stop 
> an application from crashing.  What will a test case prove?

In this case, just that the prototype is correct and so won't crash the 
program in random ways when the function is called.

-- 
Rob Shearman