Tweaks to build with VS 2013 Express

I made a couple of tweaks to get FreeImage to build out of the box using VS2013 Express.  I'm by no means a Windows developer, so I'm not sure of the correctness of these changes, but they work for me.  With these changes in place, I can build like so:

    msbuild FreeImage.2013.sln /p:Configuration=Release
    msbuild FreeImage.2013.sln /p:Configuration=Debug