package/openvpn: security bump to 2.4.2

Fixes CVE-2017-7478 & CVE-2017-7479:
https://community.openvpn.net/openvpn/wiki/QuarkslabAndCryptographyEngineerAudits

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/openvpn/openvpn.hash

@@ -1,2 +1,2 @@
 # Locally calculated
-sha256 fde9e22c6df7a335d2d58c6a4d5967be76df173c766a5c51ece57fd044c76ee5  openvpn-2.4.1.tar.xz
+sha256 df5c4f384b7df6b08a2f6fa8a84b9fd382baf59c2cef1836f82e2a7f62f1bff9  openvpn-2.4.2.tar.xz

package/openvpn/openvpn.mk

@@ -4,7 +4,7 @@
 #
 ################################################################################
 
-OPENVPN_VERSION = 2.4.1
+OPENVPN_VERSION = 2.4.2
 OPENVPN_SOURCE = openvpn-$(OPENVPN_VERSION).tar.xz
 OPENVPN_SITE = http://swupdate.openvpn.net/community/releases
 OPENVPN_DEPENDENCIES = host-pkgconf openssl