ZF-7711: Progress_key for file upload should be taken from php.ini
The render() method of Zend_Form_Decorator_File add a progress_key to track file uploads if APC or upload_progress is available. If APC is available, the progress_key is set to APC_UPLOAD_PROGRESS. However, this value should not be hard-coded, as it is configurable in the php.ini file by the apc.rfc1867_name setting.
Ideally, Zend_Form_Decorator_File should read out the apc.rfc1867_name setting from the php.ini and use that value.