stplib: support OF 1.2/1.3

ryu/lib/stplib.py : Support OpenFlow 1.2/1.3
ryu/app/simple_switch_stp.py : Correspondence to parameter change of stplib.EventPortStateChange

Signed-off-by: WATANABE Fumitaka <watanabe.fumitaka@nttcom.co.jp>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>