Added <SpecificVersion>True</SpecificVersion> so that VS2012 can build the project

This also allows assemblies referencing this to build from the command line via msbuild version 12, but not requiring the full install of VisualStudio 2013

Author: 7sharp9

src/fsharp/FSharp.Compiler.Service/FSharp.Compiler.Service.fsproj

@@ -597,10 +597,15 @@
     <Reference Include="Microsoft.Build" Condition=" '$(TargetFrameworkVersion)' == 'v4.0'" />
     <Reference Include="Microsoft.Build.Utilities.v4.0" Condition=" '$(TargetFrameworkVersion)' == 'v4.0'" />
     <Reference Include="Microsoft.Build.Tasks.v4.0" Condition=" '$(TargetFrameworkVersion)' == 'v4.0'" />
-    
-    <Reference Include="Microsoft.Build.Framework, Version=12.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" Condition=" '$(TargetFrameworkVersion)' == 'v4.5'" />
-    <Reference Include="Microsoft.Build.Engine, Version=12.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" Condition=" '$(TargetFrameworkVersion)' == 'v4.5'" />
-    <Reference Include="Microsoft.Build, Version=12.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" Condition=" '$(TargetFrameworkVersion)' == 'v4.5'" />
+    <Reference Include="Microsoft.Build.Framework, Version=12.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" Condition=" '$(TargetFrameworkVersion)' == 'v4.5'" >
+        <SpecificVersion>True</SpecificVersion>
+    </Reference>
+    <Reference Include="Microsoft.Build.Engine, Version=12.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" Condition=" '$(TargetFrameworkVersion)' == 'v4.5'" >
+        <SpecificVersion>True</SpecificVersion>
+    </Reference>
+    <Reference Include="Microsoft.Build, Version=12.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" Condition=" '$(TargetFrameworkVersion)' == 'v4.5'" >
+        <SpecificVersion>True</SpecificVersion>
+    </Reference>
     <Reference Include="Microsoft.Build.Utilities.v12.0" Condition=" '$(TargetFrameworkVersion)' == 'v4.5'" />
     <Reference Include="Microsoft.Build.Tasks.v12.0" Condition=" '$(TargetFrameworkVersion)' == 'v4.5'" />
     <Reference Include="FSharp.Core, Version=$(TargetFSharpCoreVersion), Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a">