Fix VS2013 project files

Last commit was on mac so I was unable to incude the VS project files
additions for threading-windows.c.

vs/2013/libobs/libobs.vcxproj

@@ -119,6 +119,7 @@
     <ClCompile Include="..\..\..\libobs\util\platform-windows.c" />
     <ClCompile Include="..\..\..\libobs\util\platform.c" />
     <ClCompile Include="..\..\..\libobs\util\text-lookup.c" />
+    <ClCompile Include="..\..\..\libobs\util\threading-windows.c" />
     <ClCompile Include="..\..\..\libobs\util\utf8.c" />
   </ItemGroup>
   <PropertyGroup Label="Globals">

vs/2013/libobs/libobs.vcxproj.filters

@@ -359,5 +359,8 @@
     <ClCompile Include="..\..\..\libobs\media-io\video-frame.c">
       <Filter>media-io\Source Files</Filter>
     </ClCompile>
+    <ClCompile Include="..\..\..\libobs\util\threading-windows.c">
+      <Filter>util\Source Files</Filter>
+    </ClCompile>
   </ItemGroup>
 </Project>