gnutls: bump to version 3.1.8

Fixes a regression in 3.1.7 regarding the priority string NORMAL.

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

package/gnutls/gnutls.mk

@@ -4,7 +4,7 @@
 #
 #############################################################
 
-GNUTLS_VERSION = 3.1.7
+GNUTLS_VERSION = 3.1.8
 GNUTLS_SOURCE = gnutls-$(GNUTLS_VERSION).tar.xz
 GNUTLS_SITE = ftp://ftp.gnutls.org/gcrypt/gnutls/v3.1
 GNUTLS_LICENSE = GPLv3+ LGPLv3