Change jerry_port interface to allow for a correct implementation of timezones. (#2540)

The previous jerry_port interface did not allow timezones to be handled correctly,
even if the host system was up to the task. This PR changes the jerry_port interface
to allow a completely correct implementation to exist, and provides one (for Linux/BSD
systems) in default-date.c.

Fixes #1661

JerryScript-DCO-1.0-Signed-off-by: crazy2be crazy1be@gmail.com

targets/curie_bsp/source/curie-bsp-port.c

@@ -52,16 +52,13 @@ void jerry_port_fatal (jerry_fatal_code_t code)
 } /* jerry_port_fatal */
 
 /**
- * Curie BSP implementation of jerry_port_get_time_zone.
+ * Curie BSP implementation of jerry_port_get_local_time_zone_adjustment.
  */
-bool jerry_port_get_time_zone (jerry_time_zone_t *tz_p)
+double jerry_port_get_local_time_zone_adjustment (double unix_ms, bool is_utc)
 {
   //EMPTY implementation
-  tz_p->offset = 0;
-  tz_p->daylight_saving_time = 0;
-
-  return true;
-} /* jerry_port_get_time_zone */
+  return 0;
+} /* jerry_port_get_local_time_zone_adjustment */
 
 /**
  * Curie BSP implementation of jerry_port_get_current_time.