Supported runtime v4.0 in app.config after upgrading VS11 Beta to VS2012 RC

After upgrading from VS11 Beta to VS2012 RC - I've modified from targeting .NET 4.0 to .NET 4.5. I notice in app.config following section

<startup>
    <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5" />
</startup>

What is the above for?

When I tried to create a new project (not upgrade of existing project) from within VS2012 RC I don't see the above section in app.config