Replaced deprecated-in-PHP5.5 preg_replace plus e-modifier call with pre...

In PHP5.5, the 'e' modifier for preg_replace has been deprecated.  This means that EActiveResoruceResponse::parseHeaders() errors out.  

I have replaced that call with code that uses preg_replace_callback (taken from https://stackoverflow.com/questions/15454220/replace-preg-replace-e-modifier-with-preg-replace-callback).  This code now works in PHP 5.5.  In addition, I have tested this code in PHP5.4 and it works for me.