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
Update FSharp.Compiler.Service.fsproj
Merge pull request #263 from 7sharp9/patch-1

Added <SpecificVersion>True</SpecificVersion> so that VS2012 can build t...