include filename.h even when zlib support hasn't been compiled in

panda/src/downloader/download_utils.h

@@ -16,11 +16,10 @@
 #define DOWNLOAD_UTILS_H
 
 #include "pandabase.h"
+#include "filename.h"
 
 #ifdef HAVE_ZLIB
 
-#include "filename.h"
-
 BEGIN_PUBLISH
 
 EXPCL_PANDAEXPRESS unsigned long check_crc(Filename name);