Fix old-style function definitions and enable warning. (#1651)

Function definitions with no parameters should always use the void keyword to allow the compiler to catch invalid calls of those functions at compile time.

Enable -Wold-style-definition to catch this early in the future.

Fixes #1649.

JerryScript-DCO-1.0-Signed-off-by: Tilmann Scheller t.scheller@samsung.com

targets/zephyr/src/jerry-port.c

@@ -65,7 +65,7 @@ void jerry_port_fatal (jerry_fatal_code_t code)
  * @return current timer's counter value in milliseconds
  */
 double
-jerry_port_get_current_time ()
+jerry_port_get_current_time (void)
 {
   int64_t ms = k_uptime_get();
   return (double) ms;