autoloader needs return, plugins should be required not included

inc/load.php

@@ -125,9 +125,10 @@ function load_autoload($name){
         $c = ((count($m) === 4) ? "/{$m[3]}" : '');
         $plg = DOKU_PLUGIN . "{$m[2]}/{$m[1]}$c.php";
         if(file_exists($plg)){
-            include $plg;
+            require $plg;
         }
         return true;
     }
+    return false;
 }