imm32: rework storage of thread default contexts

[Aric Stewart]

I think for threadproc function it should be WINAPI or CALLBACK.

DWORD WINAPI ThreadProc(
   __in  LPVOID lpParameter
);


yes. I should set the test to be static.

-aric

André Hentschel wrote:
> Hi Aric,
> You should have a second look at the Function heads in the tests (imm32.c).
> I doubt WINAPI should be used and the functions should be static.