Code Contracts exist on SL4, use the real bits instead

ReactiveXaml/ContractStubs.cs

@@ -1,6 +1,6 @@
 using System;
 
-#if SILVERLIGHT || DOTNETISOLDANDSAD
+#if DOTNETISOLDANDSAD
 
 namespace System.Diagnostics.Contracts
 {

ReactiveXaml/ReactiveXaml_SL4.csproj

@@ -77,7 +77,6 @@
     <Reference Include="System.Windows.Browser" />
   </ItemGroup>
   <ItemGroup>
-    <Compile Include="ContractStubs.cs" />
     <Compile Include="Interfaces.cs" />
     <Compile Include="Logging.cs" />
     <Compile Include="MemoizingMRUCache.cs" />