Add time and time zone to EXDATEs of DATE-TIME instances

KOrganizer creates DATE values for exceptions to recurring instances, even if the incidence is not "all day" (i.e. DTSTART is a DATE-TIME value). EXDATE identifies a specific instance and arguably should follow the same rules as RECURRENCE-ID. RFC 5545 does not say so, but erratum 6316 does. In practice, other important systems reject EXDATEs that do not match DTSTART.

See also incidenceeditor!15 (merged).

Original patch written by Jochen.Trumpf@anu.edu.au.

BUG: 169336 BUG: 434599 FIXED-IN: 5.17.0