Introduce the Date Port API

Replaced `gettimeofday`-related code with `jerry_port_get_current_time`
and `jerry_port_get_time_zone` function calls. Moved old code to
default port implementation.

Removed `ENABLE_DATE_SYS_CALLS` as date syscalls should "just work".

Fix DST adjustments: even if `gettimeofday` returns meaningful data in
`tz_dsttime`, the value is just a flag (or, according to some sources,
a tri-state value: >0 if DST applies, ==0 if DST does not apply, <0 if
unknown). Hitherto, the field was simply added to/subtracted from a
time value in milliseconds. To use it approximately correctly, the
field's value should be multiplied by "millisecs/hour".

JerryScript-DCO-1.0-Signed-off-by: Akos Kiss akiss@inf.u-szeged.hu

jerry-core/jerry-port.h

@@ -17,6 +17,8 @@
 #ifndef JERRY_PORT_H
 #define JERRY_PORT_H
 
+#include <stdbool.h>
+#include <stdint.h>
 #include <stdio.h>
 
 #ifdef __cplusplus
@@ -71,6 +73,34 @@ typedef enum
  */
 void jerry_port_fatal (jerry_fatal_code_t code);
 
+/*
+ * Date Port API
+ */
+
+/**
+ * Jerry time zone structure
+ */
+typedef struct
+{
+  int offset;                /**< minutes from west */
+  int daylight_saving_time;  /**< daylight saving time (1 - DST applies, 0 - not on DST) */
+} jerry_time_zone_t;
+
+/**
+ * Get timezone and daylight saving data
+ *
+ * @return true  - if success
+ *         false - otherwise
+ */
+bool jerry_port_get_time_zone (jerry_time_zone_t *tz_p);
+
+/**
+ * Get system time
+ *
+ * @return milliseconds since Unix epoch
+ */
+uint64_t jerry_port_get_current_time (void);
+
 /**
  * @}
  */