gnutls: bump to version 3.4.15

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/gnutls/gnutls.hash

@@ -1,2 +1,2 @@
 # Locally calculated after checking pgp signature
-sha256	35deddf2779b76ac11057de38bf380b8066c05de21b94263ad5b6dfa75dfbb23	gnutls-3.4.14.tar.xz
+sha256	eb2a013905f5f2a0cbf7bcc1d20c85a50065063ee87bd33b496c4e19815e3498	gnutls-3.4.15.tar.xz

package/gnutls/gnutls.mk

@@ -5,7 +5,7 @@
 ################################################################################
 
 GNUTLS_VERSION_MAJOR = 3.4
-GNUTLS_VERSION = $(GNUTLS_VERSION_MAJOR).14
+GNUTLS_VERSION = $(GNUTLS_VERSION_MAJOR).15
 GNUTLS_SOURCE = gnutls-$(GNUTLS_VERSION).tar.xz
 GNUTLS_SITE = ftp://ftp.gnutls.org/gcrypt/gnutls/v$(GNUTLS_VERSION_MAJOR)
 # README says that the core library is under LGPLv2.1+, but a few