Revert "Removed redundancy in F# project files."

This reverts commit da13cb97bf96c97362a2a5168bb34fc4819825e5.

src/FSharp/FSharp.fsproj

@@ -57,6 +57,7 @@
     <Compile Include="Matrix.fs" />
   </ItemGroup>
   <Import Project="$(MSBuildExtensionsPath32)\FSharp\1.0\Microsoft.FSharp.Targets" Condition="!Exists('$(MSBuildToolsPath)\Microsoft.Build.Tasks.v4.0.dll')" />
+  <Import Project="$(MSBuildExtensionsPath32)\..\Microsoft F#\v4.0\Microsoft.FSharp.Targets" Condition="Exists('$(MSBuildToolsPath)\Microsoft.Build.Tasks.v4.0.dll')" />
   <!-- To modify your build process, add your task inside one of the targets below and uncomment it. 
 	     Other similar extension points exist, see Microsoft.Common.targets.
 	<Target Name="BeforeBuild">

src/FSharpExamples/FSharpExamples.fsproj

@@ -58,6 +58,7 @@
     <Compile Include="MCMC.fs" />
   </ItemGroup>
   <Import Project="$(MSBuildExtensionsPath32)\FSharp\1.0\Microsoft.FSharp.Targets" Condition="!Exists('$(MSBuildToolsPath)\Microsoft.Build.Tasks.v4.0.dll')" />
+  <Import Project="$(MSBuildExtensionsPath32)\..\Microsoft F#\v4.0\Microsoft.FSharp.Targets" Condition="Exists('$(MSBuildToolsPath)\Microsoft.Build.Tasks.v4.0.dll')" />
   <!-- To modify your build process, add your task inside one of the targets below and uncomment it. 
 	     Other similar extension points exist, see Microsoft.Common.targets.
 	<Target Name="BeforeBuild">

src/FSharpUnitTests/FSharpUnitTests.fsproj

@@ -31,6 +31,7 @@
     <WarningLevel>3</WarningLevel>
   </PropertyGroup>
   <Import Project="$(MSBuildExtensionsPath32)\FSharp\1.0\Microsoft.FSharp.Targets" Condition="!Exists('$(MSBuildToolsPath)\Microsoft.Build.Tasks.v4.0.dll')" />
+  <Import Project="$(MSBuildExtensionsPath32)\..\Microsoft F#\v4.0\Microsoft.FSharp.Targets" Condition="Exists('$(MSBuildToolsPath)\Microsoft.Build.Tasks.v4.0.dll')" />
   <ItemGroup>
     <Compile Include="FsUnit.fs" />
     <Compile Include="Program.fs" />