lib ofctl_v1_2: add VLAN_ID setting means

This patch contains the following update for ofctl_v1_2 library.
 adding a means which sets up VLAN_ID.

 (I think that I will use this by a firewall Ryu application.)

Signed-off-by: TAKESHITA Noboru <takeshita.noboru@yes.nttcom.ne.jp>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
of1.0: fix NXActionHeader typo

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>