unbound: add root zone file cache option

Add the possibility to use Unbound auto-zone: clause to
fetch complete root, arpa, in-addr.arpa, and ip6.arpa
zone files. This can speed up recursion when users
access many ccTLD or connection logging hits many PTR.

Signed-off-by: Eric Luehrsen <ericluehrsen@hotmail.com>

net/unbound/Makefile

@@ -9,7 +9,7 @@ include $(TOPDIR)/rules.mk
 
 PKG_NAME:=unbound
 PKG_VERSION:=1.7.1
-PKG_RELEASE:=2
+PKG_RELEASE:=3
 
 PKG_LICENSE:=BSD-3-Clause
 PKG_LICENSE_FILES:=LICENSE