add missing reference - windows gsmopen

src/mod/endpoints/mod_gsmopen/mod_gsmopen.2010.vcxproj

@@ -160,6 +160,9 @@ rpcrt4.lib  "..\..\..\..\debug\libtiff.lib" "..\..\..\..\libs\spandsp\src\debug\
     <ClCompile Include="mod_gsmopen.cpp" />
   </ItemGroup>
   <ItemGroup>
+    <ProjectReference Include="..\..\..\..\w32\Library\FreeSwitchCore.2010.vcxproj">
+      <Project>{202d7a4e-760d-4d0e-afa1-d7459ced30ff}</Project>
+    </ProjectReference>
     <ProjectReference Include="gsmlib\gsmlib-1.10-patched-13ubuntu\win32\gsmlib.2010.vcxproj">
       <Project>{26c82fce-e0cf-4d10-a00c-d8e582ffeb53}</Project>
     </ProjectReference>