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

Makefile

@@ -76,12 +76,6 @@ BUILD_NAME:=
    BUILD_NAME:=$(BUILD_NAME)-LOG-$(LOG)
   endif
 
- # Date system calls
-  ifneq ($(DATE_SYS_CALLS),)
-   CMAKE_DEFINES:=$(CMAKE_DEFINES) -DENABLE_DATE_SYS_CALLS=$(DATE_SYS_CALLS)
-   BUILD_NAME:=$(BUILD_NAME)-DATE_SYS_CALLS-$(DATE_SYS_CALLS)
-  endif
-
  # Fill error messages for builtin error objects
   ifneq ($(ERROR_MESSAGES),)
    CMAKE_DEFINES:=$(CMAKE_DEFINES) -DENABLE_ERROR_MESSAGES=$(ERROR_MESSAGES)
@@ -106,7 +100,7 @@ BUILD_NAME:=
   endif
 
 # For testing build-options
-export BUILD_OPTIONS_TEST_NATIVE := LTO LOG DATE_SYS_CALLS ERROR_MESSAGES ALL_IN_ONE VALGRIND VALGRIND_FREYA COMPILER_DEFAULT_LIBC
+export BUILD_OPTIONS_TEST_NATIVE := LTO LOG ERROR_MESSAGES ALL_IN_ONE VALGRIND VALGRIND_FREYA COMPILER_DEFAULT_LIBC
 
 # Directories
 export ROOT_DIR := $(shell pwd)