DateInterval: fix the way the total number of days is computed to match PHP implementation (for %a)
DateInterval: fix the way the total number of days is computed to match PHP implementation (for %a)

iolevel/peachpie-concept,peachpiecompiler/peachpie,peachpiecompiler/peachpie,iolevel/peachpie-concept,iolevel/peachpie-concept,peachpiecompiler/peachpie