Add new subscription-ipp.c to Visual Studio project.
<ClCompile Include="..\pappl\resource.c" />
<ClCompile Include="..\pappl\snmp.c" />
<ClCompile Include="..\pappl\subscription.c" />
+ <ClCompile Include="..\pappl\subscription-ipp.c" />
<ClCompile Include="..\pappl\system-accessors.c" />
<ClCompile Include="..\pappl\system-ipp.c" />
<ClCompile Include="..\pappl\system-loadsave.c" />
