only compare whether the saves are equal to 0
and not their actual values.
This allows one to compare against the binary database
which does not contain actual values of save.
* The get_info functions were not prepared for the case where the start
and end times of a rule are chronologically reversed for a year. I.e.
the daylight saving start comes later in the year than the daylight
saving end. When save is positive, this happens in the southern
hemisphere (e.g. "Australia/Sydney" -> "AEST-10AEDT,M10.1.0,M4.1.0/3").
It also happens in the nothern hemisphere when the save is negative
(e.g. "Europe/Dublin" -> "IST-1GMT0,M10.5.0,M3.5.0/1").
* Added tests for Posix::time_zone.