[ZF-8470] add comment of return value to setEncoding

git-svn-id: http://framework.zend.com/svn/framework/standard/trunk@19416 44c647ce-9c0f-0410-b52a-842ac1e357ba

library/Zend/Filter/StringToLower.php

@@ -76,6 +76,7 @@ class Zend_Filter_StringToLower implements Zend_Filter_Interface
      * Set the input encoding for the given string
      *
      * @param  string $encoding
+     * @return Zend_Filter_StringToLower Provides a fluent interface
      * @throws Zend_Filter_Exception
      */
     public function setEncoding($encoding = null)

library/Zend/Filter/StringToUpper.php

@@ -76,6 +76,7 @@ class Zend_Filter_StringToUpper implements Zend_Filter_Interface
      * Set the input encoding for the given string
      *
      * @param  string $encoding
+     * @return Zend_Filter_StringToUpper Provides a fluent interface
      * @throws Zend_Filter_Exception
      */
     public function setEncoding($encoding = null)