gnutls: security bump to version 3.5.13

Fixes CVE-2017-7507: decoding a status request TLS extension that has a
non-empty responder IDs list could lead to a crash due to a null pointer
dereference.

https://lists.gnupg.org/pipermail/gnutls-devel/2017-June/008446.html

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
(cherry picked from commit 5cbf8baaa89b7ea9db855c9a9f96a4966e1e44a1)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/gnutls/gnutls.hash

@@ -1,2 +1,2 @@
 # Locally calculated after checking pgp signature
-sha256	63cb39a5eaa029381df2e49a74cfb7be89fc4a592445191818ffe1e66bde57cb	gnutls-3.5.12.tar.xz
+sha256	79f5480ad198dad5bc78e075f4a40c4a315a1b2072666919d2d05a08aec13096	gnutls-3.5.13.tar.xz

package/gnutls/gnutls.mk

@@ -5,7 +5,7 @@
 ################################################################################
 
 GNUTLS_VERSION_MAJOR = 3.5
-GNUTLS_VERSION = $(GNUTLS_VERSION_MAJOR).12
+GNUTLS_VERSION = $(GNUTLS_VERSION_MAJOR).13
 GNUTLS_SOURCE = gnutls-$(GNUTLS_VERSION).tar.xz
 GNUTLS_SITE = ftp://ftp.gnutls.org/gcrypt/gnutls/v$(GNUTLS_VERSION_MAJOR)
 GNUTLS_LICENSE = LGPL-2.1+ (core library), GPL-3.0+ (gnutls-openssl library)