[banshee] AppleDevice: add missing reference in project file

[AndrÃs Aragoneses <aaragoneses src gnome org>]

commit 61f76bd22834201b0ccbdbc39d23b6be81140213
Author: Andres G. Aragoneses <knocte gmail com>
Date:   Sat Apr 21 20:59:23 2012 +0100

    AppleDevice: add missing reference in project file
    
    Thanks to this, MonoDevelop (master branch) stops reporting some elements as missing (red). This would help the build in MS.NET in theory as well.

 .../Banshee.Dap.AppleDevice.csproj                 |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/src/Dap/Banshee.Dap.AppleDevice/Banshee.Dap.AppleDevice.csproj b/src/Dap/Banshee.Dap.AppleDevice/Banshee.Dap.AppleDevice.csproj
index b5acbcc..2b06add 100644
--- a/src/Dap/Banshee.Dap.AppleDevice/Banshee.Dap.AppleDevice.csproj
+++ b/src/Dap/Banshee.Dap.AppleDevice/Banshee.Dap.AppleDevice.csproj
@@ -80,6 +80,7 @@
     <Reference Include="libgpod-sharp, Version=1.0.3824.40135, Culture=neutral">
       <Package>libgpod-sharp</Package>
     </Reference>
+    <Reference Include="System.Core" />
   </ItemGroup>
   <ItemGroup>
     <EmbeddedResource Include="Banshee.Dap.AppleDevice.addin.xml">