table/chain: add u8 setter and getter for family values

These are needed to set the family value for chain and table.

Signed-off-by: Ana Rey <anarey@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
tests: add unit tests for libnftables

These tests create an initial object 'a' whose attributes are
set to arbitrary values. Then, that object is converted to a
Netlink message which is parsed to obtain the object 'b'. If
things go well, the original object 'a' and the transformed
object 'b' should be equivalent. Thus, we make sure that object
transformations through the main library APIs are correct.

These tests have helped to catch the following bugs in this library:

(3cf788a72 expr: fix leak in target and match expressions)
(4182e574f expr: match: fix wrong flag setting in nft_rule_expr_match_parse)
(0bec6bc5e expr: log: release prefix)
(2b690deea expr: log: fix missing \0 when sending log prefix to kernel)
(e55c7afcf expr: target: fix wrong info length in nft_rule_expr_target_parse)
(8fc4d4bd2 expr: log: fix wrong attribute type in nft_rule_expr_log_parse)

Signed-off-by: Ana Rey <anarey@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>