url-http-ntlm: Override url-http-parse-headers redirect handling

* url-http-ntlm.el: Require versioned url-http-ntlm-parse-headers
feature when emacs-major-version is less than 25.
* url-http-ntlm-parse-headers-24.1.el,
url-http-ntlm-parse-headers-24.2.el,
url-http-ntlm-parse-headers-24.3.el,
url-http-ntlm-parse-headers-24.4.el,
url-http-ntlm-parse-headers-24.5.el: New files.