Make gnutls-negotiate ignore specially handled files

Fixes: debbugs:15866

* lisp/net/gnutls.el (gnutls-negotiate): Ignore files found via
'file-name-handler-alist' since the gnutls library can't use those.

lisp/ChangeLog

+2014-12-08  Lars Magne Ingebrigtsen  <larsi@gnus.org>
+
+	* net/gnutls.el (gnutls-negotiate): Ignore files found via
+	'file-name-handler-alist' since the gnutls library can't use those
+	(bug#15866).
+
 2014-12-08  Dmitry Gutov  <dgutov@yandex.ru>
 
 	* vc/vc-hg.el (vc-hg-dir-status-files): Only include ignores files

lisp/net/gnutls.el

@@ -189,6 +189,9 @@ here's a recent version of the list.
 It must be omitted, a number, or nil; if omitted or nil it
 defaults to GNUTLS_VERIFY_ALLOW_X509_V1_CA_CRT."
   (let* ((type (or type 'gnutls-x509pki))
+	 ;; The gnutls library doesn't understand files delivered via
+	 ;; the special handlers, so ignore all files found via those.
+	 (file-name-handler-alist nil)
          (trustfiles (or trustfiles
                          (delq nil
                                (mapcar (lambda (f) (and f (file-exists-p f) f))