[1/2] dpnet: Add IDirectPlay8Client tests

[Alistair Leslie-Hughes]

> Please avoid such dependencies between different tests. If creating and releasing the client is something that every test has to do you can add helper functions for this task.
A usual approach is to only have a single client, so I've changed the 
init function to fail if we don't have a client pointer.

>> +    hr = IDirectPlay8Client_CancelAsyncOperation(client, async, 0);
>> +    ok(hr == S_OK, "IDirectPlay8Client_CancelAsyncOperation failed with 0x%08x\n", hr);
> Are you sure that this always returns DPNSUCCESS_PENDING? Couldn't it also return a result instantly? Overall I don't see the point in this test at the moment. As it is now it doesn't say much. This is just an opinion though, I'll leave the decision up to you.
Since we are running asynchronously, this is the default return value.

>
>> +    todo_wine ok(caps.dwMaxEnumPayloadSize == 983, "expected 983, got %d\n", caps.dwMaxEnumPayloadSize);
> Out of curiosity, do you have any idea where this value comes from?
No, I don't know where these value come from.  However they seem to be 
same between windows versions.

Best Regards
  Alistair Leslie-Hughes