libical 4 changed several APIs used by GNOME Calendar:
- libical-glib now provides autoptr cleanup for ICalTime, so only
define it ourselves for older versions.
- i_cal_recurrence_get/set_by_day() were removed in favor of the
dynamically sized by-rule arrays; add local helpers on top of
i_cal_recurrence_get/set_by().
- i_cal_errno_return() was renamed to i_cal_error_icalerrno().
Also make the create-tzid event test independent of line folding,
which differs between libical versions.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>