packet/zebra: Support some FRRouting messages format
packet/zebra: Support some FRRouting messages format

Note: This patch does not support all messages defined in FRRouting,
and some of message are left on TODO.

Signed-off-by: IWASE Yusuke <bb80e84cc9f5a8f01385872ee89032beb5d4eba7@gmail.com>
Signed-off-by: FUJITA Tomonori <93dac1fe9c4b2a3957982200319981492ad4976e@lab.ntt.co.jp>

osrg/ryu,lagopus/ryu-lagopus-ext,iwaseyusuke/ryu,iwaseyusuke/ryu,lagopus/ryu-lagopus-ext,iwaseyusuke/ryu,osrg/ryu,iwaseyusuke/ryu,fujita/ryu,fujita/ryu,lagopus/ryu-lagopus-ext,iwaseyusuke/ryu,osrg/ryu,fujita/ryu,fujita/ryu,lagopus/ryu-lagopus-ext,lagopus/ryu-lagopus-ext,fujita/ryu,osrg/ryu,osrg/ryu