Expose information whether a timezone offset has been explicitly set on DateTime object
For some applications it would be beneficial if Ruby would expose information on whether a DateTime object has an explicitly set timezone offset. An application might want to use DateTimes that don't concern themselves with timezone offsets and don't perform conversions between zones. To make this backwards compatible I'd suggest to expose a flag on whether an offset has been set or whether the default (offset=0) has been automatically assumed. An application might then decide to handle a DateTime that has the default timezone offset automatically assumed (offset=0) differently from a DateTime that has UTC (offset=0) set explicitly.