add date/time functions (some of these)

* define FOXWAY_DOUBLE_ARROW_WAS_USED (in compiler)
* allows define constants as function (in runtime)

Time: 474 ms, Memory: 24.50Mb
OK (478 tests, 484 assertions)

Change-Id: Id584dae5c7458a2c88becbae2d880fecc39160b5