[Zend_App] Added notice for fellow contributors why there's only been one parameter given to class_exists(); #ZF-7550 & #ZF-8427 & #ZF-8424

git-svn-id: http://framework.zend.com/svn/framework/standard/trunk@19316 44c647ce-9c0f-0410-b52a-842ac1e357ba

library/Zend/Application/Bootstrap/BootstrapAbstract.php

@@ -351,7 +351,7 @@ abstract class Zend_Application_Bootstrap_BootstrapAbstract
                 }
             }
 
-            if (class_exists($plugin)) {
+            if (class_exists($plugin)) { //@SEE ZF-7550
                 $spec = (array) $spec;
                 $spec['bootstrap'] = $this;
                 $instance = new $plugin($spec);