stunnel: add STUNNEL_VERSION_MAJOR variable

Signed-off-by: Jerzy Grzegorek <jerzy.grzegorek@trzebnica.net>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/stunnel/stunnel.mk

@@ -4,8 +4,9 @@
 #
 ################################################################################
 
-STUNNEL_VERSION = 5.17
-STUNNEL_SITE = http://www.usenix.org.uk/mirrors/stunnel/archive/5.x
+STUNNEL_VERSION_MAJOR = 5
+STUNNEL_VERSION = $(STUNNEL_VERSION_MAJOR).17
+STUNNEL_SITE = http://www.usenix.org.uk/mirrors/stunnel/archive/$(STUNNEL_VERSION_MAJOR).x
 STUNNEL_DEPENDENCIES = openssl
 STUNNEL_CONF_OPTS = --with-ssl=$(STAGING_DIR)/usr --with-threads=fork \
 	--disable-libwrap