datapath-windows: Enable multiprocessor compilation on solution

Visual Studio defines by default the maximum number of concurrent jobs.

This patch allows the parallel built of the solution.

Signed-off-by: Alin Gabriel Serdean <aserdean@cloudbasesolutions.com>
Acked-by: Sairam Venugopal <vsairam@vmware.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>

datapath-windows/ovsext/ovsext.vcxproj

@@ -164,6 +164,10 @@
       <AdditionalIncludeDirectories Condition="'$(Configuration)|$(Platform)'=='Win8.1 Debug|x64'">$(IntDir);%(AdditionalIncludeDirectories);..\..</AdditionalIncludeDirectories>
       <AdditionalIncludeDirectories Condition="'$(Configuration)|$(Platform)'=='Win8 Release|x64'">$(IntDir);%(AdditionalIncludeDirectories);..\..</AdditionalIncludeDirectories>
       <AdditionalIncludeDirectories Condition="'$(Configuration)|$(Platform)'=='Win8.1 Release|x64'">$(IntDir);%(AdditionalIncludeDirectories);..\..</AdditionalIncludeDirectories>
+      <MultiProcessorCompilation Condition="'$(Configuration)|$(Platform)'=='Win8 Release|x64'">true</MultiProcessorCompilation>
+      <MultiProcessorCompilation Condition="'$(Configuration)|$(Platform)'=='Win8 Debug|x64'">true</MultiProcessorCompilation>
+      <MultiProcessorCompilation Condition="'$(Configuration)|$(Platform)'=='Win8.1 Debug|x64'">true</MultiProcessorCompilation>
+      <MultiProcessorCompilation Condition="'$(Configuration)|$(Platform)'=='Win8.1 Release|x64'">true</MultiProcessorCompilation>
     </ClCompile>
   </ItemDefinitionGroup>
   <ItemGroup>