test case demonstrating PeekMessage give up timeslices

[Felix Nawothnig]

Alexandre Julliard wrote:
>>So, PeekMessage always yields execution (it shouldn't) with PM_NOYIELD
>>specified it yields execution twice (although it shouldn't at all).
> PeekMessage is going to call the server and wait on the result,
> there's no way around it. The extra yield is to avoid hammering the
> server with requests in stupid apps that constantly poll for messages,

But then that "extra" NtYieldExecution should not depend on !PM_NOYIELD 
since PM_NOYIELD doesn't have any effect on Windows, right?

> since a server call is much more expensive than a Windows system call.

Would using shm fix that?

Felix