Fixed compiler warnings.

src/archiver_iso9660.c

@@ -314,7 +314,8 @@ static int parseVolumeDescriptor(PHYSFS_Io *io, PHYSFS_uint64 *_rootpos,
 
 static void *ISO9660_openArchive(PHYSFS_Io *io, const char *filename, int forWriting)
 {
-    PHYSFS_uint64 rootpos, len;
+    PHYSFS_uint64 rootpos = 0;
+    PHYSFS_uint64 len = 0;
     int joliet = 0;
     void *unpkarc = NULL;