minor, catch leap transitions in dt_dtadd() when real-seconds/minutes/hours/days are requested
minor, catch leap transitions in dt_dtadd() when real-seconds/minutes/hours/days are requested

Signed-off-by: Sebastian Freundt <1f0829204b3475c52f714f96be4e7b39a87b6e74@ga-group.nl>

rudimeier/dateutils,rudimeier/dateutils,rudimeier/dateutils