[Interest] Adding editable files to VS2013 project via .pro and qmake

[Tony Rietwyk]

Hi Everybody, 

I am using Qt5.5.1 and qmake to generate a project for Visual Studio 2013.
I would like to add some text files to those shown in the Solution Explorer
so that I can edit them.  They are not required for building, nor for
deployment.  

I tried adding a file in VS, and then diff'ing to the generated version.
Only one extra tag is included in the project file:  

  <ItemGroup>
    <None Include="relative_path_to_the_file_I_added" />
  </ItemGroup>

I can manually insert this section into the .vcxproj file after I run qmake.
Browsing the Qt sources, I can see this tag can be written in
msbuild_objectmodel.cpp on line 2039.  But I can't trace back through
callers to see how to execute that statement.  

Is there a syntax for my .pro to include these additional files?  

Thanks in advance! 

Tony