VS2010: adding another pre-build command to copy platform.hpp in perf/ directory

builds/msvc/libzmq/libzmq.vcxproj

@@ -102,6 +102,12 @@
     <_ProjectFileVersion>10.0.40219.1</_ProjectFileVersion>
     <CodeAnalysisRuleSet>AllRules.ruleset</CodeAnalysisRuleSet>
   </PropertyGroup>
+  <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">
+    <PreBuildEvent>
+      <Command>copy ..\platform.hpp ..\..\..\src
+copy ..\platform.hpp ..\..\..\perf</Command>
+    </PreBuildEvent>
+  </ItemDefinitionGroup>
   <ItemGroup>
     <ClCompile Include="..\..\..\src\address.cpp" />
     <ClCompile Include="..\..\..\src\clock.cpp" />