Add third_party/winsdk_samples/src to gitignore.

TBR=kjellander@webrtc.org
Review URL: https://webrtc-codereview.appspot.com/929026

git-svn-id: http://webrtc.googlecode.com/svn/trunk@3149 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/.gitignore b/.gitignore
index b82f30b..42bf048 100644
--- a/.gitignore
+++ b/.gitignore
@@ -59,6 +59,7 @@
 /third_party/opus
 /third_party/protobuf
 /third_party/valgrind
+/third_party/winsdk_samples/src
 /third_party/yasm
 /tools/clang
 /tools/gyp