Allow export to use more memory and more time.

export.php

@@ -54,6 +54,9 @@ $formparams = array('course' => $course, 'cm' => $cm, 'modcontext' => $context);
 $mform = new mod_attendance\form\export($att->url_export(), $formparams);
 
 if ($formdata = $mform->get_data()) {
+    // Exporting large courses may use a bit of memory/take a bit of time.
+    \core_php_time_limit::raise();
+    raise_memory_limit(MEMORY_HUGE);
 
     $pageparams = new mod_attendance_page_with_filter_controls();
     $pageparams->init($cm);