bgpd: add --disable-stdlog option
bgpd: add --disable-stdlog option

This enables you to write log to both stdout and syslog.

If you enable syslog, bgpd writes to both. You don't want bgpd to
write to stdout, then use this new option.

Signed-off-by: FUJITA Tomonori <93dac1fe9c4b2a3957982200319981492ad4976e@lab.ntt.co.jp>

a16/gobgp,YujiOshima/gobgp,j-kato/gobgp,tamihiro/gobgp,h-naoto/gobgp,a16/gobgp,fujita/gobgp,j-kato/gobgp,postfix/gobgp,fujita/gobgp,osrg/gobgp,a16/gobgp,Dipsingh/gobgp,osrg/gobgp,a16/gobgp,h-naoto/gobgp,ramrunner/gobgp,Dipsingh/gobgp,tamihiro/gobgp,postfix/gobgp,tamihiro/gobgp,fujita/gobgp,ishidawataru/gobgp,a16/gobgp,ishidawataru/gobgp,fujita/gobgp,a16/gobgp,postfix/gobgp,ishidawataru/gobgp,osrg/gobgp,j-kato/gobgp,osrg/gobgp,YujiOshima/gobgp,ramrunner/gobgp,tamihiro/gobgp,YujiOshima/gobgp,a16/gobgp,ramrunner/gobgp,Dipsingh/gobgp,h-naoto/gobgp