ZF-6038: Ability to remove single http header from response

Description

Hello,

If would be nice to have ability to remove separate headers by their respective names, i.e. $this->getResponse()->clearHeader('Pragma')

Comments

This patch adds two new methods to Zend_Controller_Response_Abstract with associated passing tests:

  1. clearHeader + testClearHeader
  2. clearRawHeader + testClearRawHeader

Please review -- if anything looks problematic please let me know.

Updated file extension of patch per http://framework.zend.com/wiki/display/…

Assigning to component lead per: http://framework.zend.com/wiki/display/…

Revised patch removing issue number from test name per note from ralphschindler on #zftalk.dev.

Patch applied to trunk; will release with 1.10 (new features)