server: Fix loading of IMAGE_OPTIONAL_HEADER

[Piotr Caban]

On 08/08/16 16:28, Marvin wrote:
> Hi,
>
> While running your changed tests on Windows, I think I found new failures.
> Being a bot and all I'm not very good at pattern recognition, so I might be
> wrong, but could you please double-check?
> Full results can be found at
> https://testbot.winehq.org/JobDetails.pl?Key=24836
>
> Your paranoid android.

The test failures are not caused by my patch.