MDL-30562 qtypes: extra_answer_fields & questionid_column_name public

Will let us make more of qtype backup and restore work automatically.

question/type/questiontypebase.php

@@ -165,7 +165,7 @@ public function extra_question_fields() {
      * If you use extra_question_fields, overload this function to return question id field name
      *  in case you table use another name for this column
      */
-    protected function questionid_column_name() {
+    public function questionid_column_name() {
         return 'questionid';
     }
 
@@ -176,7 +176,7 @@ protected function questionid_column_name() {
      *
      * @return mixed array as above, or null to tell the base class to do nothing.
      */
-    protected function extra_answer_fields() {
+    public function extra_answer_fields() {
         return null;
     }
 

question/type/shortanswer/questiontype.php

@@ -42,7 +42,7 @@ public function extra_question_fields() {
         return array('question_shortanswer', 'answers', 'usecase');
     }
 
-    protected function questionid_column_name() {
+    public function questionid_column_name() {
         return 'question';
     }
 

question/type/upgrade.txt

@@ -38,3 +38,8 @@ $string['pluginnameediting'] = 'Editing a Description';
 $string['pluginnamesummary'] = 'This is not actually a question. Instead it is a way to add some instructions, rubric or other content to the activity. This is similar to the way that labels can be used to add content to the course page.';
 
 The old strings will continue to work, but only until Moodle 2.3 is released.
+
+* If you are using the facilities provided by overriding the extra_answer_fields
+  or questionid_column_name methods, then you must change these to be public
+  methods. (This is required so that backup and restore can be made to work
+  automatically. MDL-24408, MDL-25617, MDL-30562)