fix compiler warning

tests/libtest/lib547.c

@@ -16,6 +16,7 @@
 
 #define UPLOADTHIS "this is the blurb we want to upload\n"
 
+#ifndef LIB548
 static size_t readcallback(void  *ptr,
                            size_t size,
                            size_t nmemb,
@@ -28,6 +29,7 @@ static size_t readcallback(void  *ptr,
   }
   return 0;
 }
+#endif
 
 int test(char *URL)
 {