Moving some types to System.Reactive.Shared.

AsyncRx.NET/System.Reactive.Async/System.Reactive.Async.csproj

@@ -12,6 +12,10 @@
     </None>
   </ItemGroup>
 
+  <ItemGroup>
+    <ProjectReference Include="..\System.Reactive.Shared\System.Reactive.Shared.csproj" />
+  </ItemGroup>
+
   <ItemGroup>
     <None Update="System\Reactive\Linq\Operators\Average.Generated.tt">
       <LastGenOutput>Average.Generated.cs</LastGenOutput>