Provide a way for the DTE to provide the IVsSolution interface.

Workaround is to have the DTE class implement the System.IServiceProvider interface which is not
actually implemented by Visual Studio's EnvDTE.DTE class.

src/AddIns/Misc/PackageManagement/Project/Src/EnvDTE/DTE.cs

@@ -5,11 +5,13 @@ using System;
 using System.Collections;
 using System.Collections.Generic;
 using System.Linq;
+
+using Microsoft.VisualStudio.Shell;
 using SD = ICSharpCode.SharpDevelop.Project;
 
 namespace ICSharpCode.PackageManagement.EnvDTE
 {
-	public class DTE : MarshalByRefObject, global::EnvDTE.DTE
+	public class DTE : MarshalByRefObject, global::EnvDTE.DTE, IServiceProvider
 	{
 		IPackageManagementProjectService projectService;
 		IPackageManagementFileService fileService;
@@ -83,5 +85,14 @@ namespace ICSharpCode.PackageManagement.EnvDTE
 		public global::EnvDTE.SourceControl SourceControl {
 			get { return null; }
 		}
+		
+		/// <summary>
+		/// HACK - EnvDTE.DTE actually implements Microsoft.VisualStudio.OLE.Interop.IServiceProvider
+		/// which is COM specific and has a QueryInterface method.
+		/// </summary>
+		object IServiceProvider.GetService(Type serviceType)
+		{
+			return Package.GetGlobalService(serviceType);
+		}
 	}
 }