Fix a problem in url.el without GnuTLS

Fixes: debbugs:19346

* lisp/url/url-http.el (url-http-parse-headers): Check that
`gnutls-available-p' is defined.

lisp/url/ChangeLog

+2014-12-11  Lars Magne Ingebrigtsen  <larsi@gnus.org>
+
+	* url-http.el (url-http-parse-headers): Check that
+	`gnutls-available-p' is defined (bug#19346).
+
 2014-12-09  Lars Magne Ingebrigtsen  <larsi@gnus.org>
 
 	* url-http.el (url-http-parse-headers): Pass the GnuTLS status of

lisp/url/url-http.el

@@ -495,7 +495,8 @@ should be shown to the user."
 				    (url-port url-current-object)
 				    url-http-process)
   ;; Pass the https certificate on to the caller.
-  (when (gnutls-available-p)
+  (when (and (fboundp 'gnutls-available-p)
+	     (gnutls-available-p))
     (let ((status (gnutls-peer-status url-http-process)))
       (when (or status
 		(plist-get (car url-callback-arguments) :peer))