Fix #467 use of core deprecated strings.

lang/en/attendance.php

@@ -575,3 +575,4 @@ $string['formattexttype'] = 'Formatting';
 $string['currentlyselectedusers'] = 'Currently selected users';
 $string['usemessageform'] = 'or use the form below to send a message to the selected students';
 $string['backtoparticipants'] = 'Back to participants list';
+$string['previewhtml'] = 'HTML format preview';

messageselect.php

@@ -131,7 +131,7 @@ if (!empty($messagebody) && !$edit && !$deluser && ($preview || $send)) {
 <input type="hidden" name="format" value="'.$format.'" />
 <input type="hidden" name="sesskey" value="' . sesskey() . '" />
 ';
-            echo "<h3>".get_string('previewhtml')."</h3>";
+            echo "<h3>".get_string('previewhtml', 'mod_attendance')."</h3>";
             echo "<div class=\"messagepreview\">\n".format_text($messagebody, $format)."\n</div>\n";
             echo '<p align="center"><input type="submit" name="send" value="'.get_string('sendmessage', 'message').'" />'."\n";
             echo '<input type="submit" name="edit" value="'.get_string('update').'" /></p>';
@@ -156,7 +156,7 @@ if (!empty($messagebody) && !$edit && !$deluser && ($preview || $send)) {
                 }
                 echo '</ul>';
             }
-            echo '<p align="center"><a href="index.php?id='.$id.'">'.get_string('backtoparticipants').'</a></p>';
+            echo '<p align="center"><a href="index.php?id='.$id.'">'.get_string('backtoparticipants', 'mod_attendance').'</a></p>';
         }
         echo $OUTPUT->footer();
         exit;