WinSDK samples: Change include path to system include to file include.

This is needed to get the GN build for Windows to pass.

BUG=4105
R=henrika@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/38439004

git-svn-id: http://webrtc.googlecode.com/svn/deps/third_party/winsdk_samples_v71@7951 4adac7df-926f-26a2-2b94-8c16560cd09d