oxcical: drop "one day" condition for allday imports

When an iCalendar file has no X-MICROSOFT-CDO-ALLDAYEVENT line, the
determination whether the event is all-day depends on the format of
DTSTART and DTEND. There is also an 1-day length check in oxcical.cpp
that also influences this, but there is no explanation given for why
it is there.

References: GXL-617, DESK-3728

Author: jengelh

lib/mapi/oxcical.cpp

@@ -2176,7 +2176,7 @@ static const char *oxcical_import_internal(const char *str_zone, const char *met
 	    start_itime.type != itime_type::utc && start_itime.hour == 0 &&
 	    start_itime.minute == 0 && start_itime.second == 0 &&
 	    end_itime.hour == 0 && end_itime.minute == 0 &&
-	    end_itime.second == 0 && end_itime.delta_day(start_itime) == 1)
+	    end_itime.second == 0)
 		b_allday = true;
 	if (b_allday && !oxcical_parse_subtype(phash, &last_propid, pmsg, pexception))
 		return "E-2704: oxcical_parse_subtype returned an unspecified error";