[f-spot] Fix Monodevelop build.

[Ruben Vermeersch <rubenv src gnome org>]

commit c857a74467d3b9b1a936e5c724c96180a273f27c
Author: Ruben Vermeersch <ruben savanne be>
Date:   Mon Sep 13 10:03:00 2010 +0200

    Fix Monodevelop build.

 src/Core/FSpot.Gui/FSpot.Gui.csproj |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/src/Core/FSpot.Gui/FSpot.Gui.csproj b/src/Core/FSpot.Gui/FSpot.Gui.csproj
index 41518ff..fa0a5b2 100644
--- a/src/Core/FSpot.Gui/FSpot.Gui.csproj
+++ b/src/Core/FSpot.Gui/FSpot.Gui.csproj
@@ -92,6 +92,7 @@
     </Reference>
     <Reference Include="System" />
     <Reference Include="Mono.Cairo" />
+    <Reference Include="System.Core" />
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\FSpot.Utils\FSpot.Utils.csproj">