addrblock: Support an optional non-strict mode accepting certs without addrblock

This allows a gateway to enforce the addrblock policy on certificates that
actually have the extension only. For (legacy) certificates not having the
extension, traffic selectors are validated/narrowed by other means, most
likely by the configuration.

conf/Makefile.am

@@ -28,6 +28,7 @@ options = \
 	options/tnc.opt
 
 plugins = \
+	plugins/addrblock.opt \
 	plugins/android_log.opt \
 	plugins/attr.opt \
 	plugins/attr-sql.opt \