add check if a page has once existed and show new onceexisted page

inc/changelog.php

@@ -743,6 +743,15 @@ abstract class ChangeLog {
 
         return array(array_reverse($revs1), array_reverse($revs2));
     }
+    
+    /**
+     * Checks if the ID has old revisons
+     * @return boolean
+     */
+    public function hasRevisions() {
+        $file = $this->getChangelogFilename();
+        return file_exists($file);
+    }
 
     /**
      * Returns lines from changelog.

inc/lang/en/onceexisted.txt

+======= This page does not exist anymore ======
+
+You've followed a link to a page that no longer exists. You can check the list of [[?do=revisions|old revisions]] to see when and why it was deleted, access old revisions or restore it.
\ No newline at end of file

inc/parserutils.php

@@ -82,7 +82,13 @@ function p_wiki_xhtml($id, $rev='', $excuse=true,$date_at=''){
         if(file_exists($file)){
             $ret = p_cached_output($file,'xhtml',$id);
         }elseif($excuse){
-            $ret = p_locale_xhtml('newpage');
+            //check if the page once existed
+            $changelog = new PageChangelog($id);
+            if($changelog->hasRevisions()) {
+                $ret = p_locale_xhtml('onceexisted');
+            } else {
+                $ret = p_locale_xhtml('newpage');
+            }
         }
     }