avoid the use of variadic macros for greater portability

lib/sendf.c

@@ -224,6 +224,10 @@ static size_t convert_lineends(struct SessionHandle *data,
 
 void Curl_infof(struct SessionHandle *data, const char *fmt, ...)
 {
+#ifdef CURL_DISABLE_VERBOSE_STRINGS
+  (void)data;
+  (void)fmt;
+#else
   if(data && data->set.verbose) {
     va_list ap;
     size_t len;
@@ -234,6 +238,7 @@ void Curl_infof(struct SessionHandle *data, const char *fmt, ...)
     len = strlen(print_buffer);
     Curl_debug(data, CURLINFO_TEXT, print_buffer, len, NULL);
   }
+#endif
 }
 
 /* Curl_failf() is for messages stating why we failed.