build: Support libical 4

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>

src/core/gcal-recurrence.c

@@ -22,6 +22,30 @@
 
 #include <glib.h>
 
+#if ICAL_MAJOR_VERSION >= 4
+/* libical 4 replaced the fixed-size by_day array with dynamically sized arrays */
+static gshort
+i_cal_recurrence_get_by_day (ICalRecurrence *rrule,
+                             guint           index)
+{
+  if (index >= i_cal_recurrence_get_by_array_size (rrule, I_CAL_BY_DAY))
+    return -1;
+
+  return i_cal_recurrence_get_by (rrule, I_CAL_BY_DAY, index);
+}
+
+static void
+i_cal_recurrence_set_by_day (ICalRecurrence *rrule,
+                             guint           index,
+                             gshort          value)
+{
+  if (index >= i_cal_recurrence_get_by_array_size (rrule, I_CAL_BY_DAY))
+    i_cal_recurrence_resize_by_array (rrule, I_CAL_BY_DAY, index + 1);
+
+  i_cal_recurrence_set_by (rrule, I_CAL_BY_DAY, index, value);
+}
+#endif
+
 G_DEFINE_BOXED_TYPE (GcalRecurrence, gcal_recurrence, gcal_recurrence_ref, gcal_recurrence_unref)
 
 static void