MDL-46681 qtype_multichoice: disabled unused options

For questions set to 'One answer only', the 'Clear incorrect responses'
and 'Show the number of correct responses' hint options make not sense,
and are not used. Hence we disableIf them.

question/type/multichoice/edit_multichoice_form.php

@@ -82,6 +82,13 @@ class qtype_multichoice_edit_form extends question_edit_form {
         return $repeated;
     }
 
+    protected function get_hint_fields($withclearwrong = false, $withshownumpartscorrect = false) {
+        list($repeated, $repeatedoptions) = parent::get_hint_fields($withclearwrong, $withshownumpartscorrect);
+        $repeatedoptions['hintclearwrong']['disabledif'] = array('single', 'eq', 1);
+        $repeatedoptions['hintshownumcorrect']['disabledif'] = array('single', 'eq', 1);
+        return array($repeated, $repeatedoptions);
+    }
+
     protected function data_preprocessing($question) {
         $question = parent::data_preprocessing($question);
         $question = $this->data_preprocessing_answers($question, true);