zebra/zapi: Support some FRRouting messages
zebra/zapi: Support some FRRouting messages

The supposed FRRouting version for this patch is 3.0 (tag name is
"frr-3.0").

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>

a16/gobgp,j-kato/gobgp,a16/gobgp,j-kato/gobgp,tamihiro/gobgp,tamihiro/gobgp,a16/gobgp,fujita/gobgp,j-kato/gobgp,fujita/gobgp,fujita/gobgp,osrg/gobgp,osrg/gobgp,tamihiro/gobgp,osrg/gobgp,a16/gobgp,tamihiro/gobgp,fujita/gobgp,a16/gobgp,osrg/gobgp,a16/gobgp,a16/gobgp