add IPv6 default route interface auto-detection for permanent/temporary IPv6 without netif

- get_default_route_netif_index(): UDP connect trick + getifaddrs to find default route iface
- etcp_socket_add(): auto-detect netif_index when not specified in config
- queue_new() API: explicit index_offset/index_size params instead of implicit from hash_size
- radix: cleanup types (uint8_t*), replace bzero/bcmp with memset/memcmp, remove kernel ifdefs
- route6_lib: new IPv6 routing library + get_node_v6_routes()

lib/Makefile.am

@@ -23,6 +23,8 @@ libuasync_a_SOURCES = \
 	swm_min.h \
 	mem.c \
 	mem.h \
+	radix.c \
+	radix.h \
 	serialize.c \
 	serialize.h