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

targets/default/jerry-port-default-date.c

@@ -0,0 +1,53 @@
+/* Copyright 2016 Samsung Electronics Co., Ltd.
+ * Copyright 2016 University of Szeged
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#define _BSD_SOURCE
+#include <sys/time.h>
+
+#include "jerry-port.h"
+#include "jerry-port-default.h"
+
+/**
+ * Default implementation of jerry_port_get_time_zone.
+ */
+bool jerry_port_get_time_zone (jerry_time_zone_t *tz_p)
+{
+  struct timeval tv;
+  struct timezone tz;
+
+  /* gettimeofday may not fill tz, so zero-initializing */
+  tz.tz_minuteswest = 0;
+  tz.tz_dsttime = 0;
+
+  gettimeofday (&tv, &tz);
+
+  tz_p->offset = tz.tz_minuteswest;
+  tz_p->daylight_saving_time = tz.tz_dsttime > 0 ? 1 : 0;
+
+  return true;
+} /* jerry_port_get_time_zone */
+
+/**
+ * Default implementation of jerry_port_get_current_time.
+ */
+uint64_t jerry_port_get_current_time ()
+{
+  struct timeval tv;
+
+  gettimeofday (&tv, NULL);
+
+  return ((uint64_t) tv.tv_sec) * 1000 + ((uint64_t) tv.tv_usec) / 1000;
+} /* jerry_port_get_current_time */