vcl: Fix cups ifdefery

So ENABLE_CUPS is defined if we want CUPS but that does not
guarantee that we actually have it installed. So use HAVE_CUPS_H
that is defined only if the cups headers are found.

Change-Id: I7c6c3659b368dbf9f8efab31ef457f41ac162160

vcl/unx/generic/printer/ppdparser.cxx

@@ -655,7 +655,7 @@ const PPDParser* PPDParser::getParser( const String& rFile )
         PrinterInfoManager& rMgr = PrinterInfoManager::get();
         if( rMgr.getType() == PrinterInfoManager::CUPS )
         {
-#ifdef ENABLE_CUPS
+#ifdef HAVE_CUPS_H
             pNewParser = const_cast<PPDParser*>(static_cast<CUPSManager&>(rMgr).createCUPSParser( aFile ));
 #endif
         }