log/syslog: add Alert method
log/syslog: add Alert method

Alert logs a message using the LOG_ALERT priority.

Fixes issue 2325.

R=mikioh.mikioh, rsc
CC=golang-dev
http://codereview.appspot.com/5504058

Committer: Mikio Hara <e2f4d2eec1d9a1f781345cdd7260d7d52e6468ae@gmail.com>

apparentlymart/golang,apparentlymart/golang,apparentlymart/golang,apparentlymart/golang,tv42/old-go,tv42/old-go,dsriram/golang,gnanderson/go,dsriram/golang,pombredanne/go-deleteme,gnanderson/go,gnanderson/go,pombredanne/go-deleteme,dsriram/golang,gnanderson/go,dsriram/golang,apparentlymart/golang,apparentlymart/golang,tv42/old-go,tv42/old-go,dsriram/golang,gnanderson/go,tv42/old-go,pombredanne/go-deleteme,dsriram/golang,tv42/old-go,pombredanne/go-deleteme,pombredanne/go-deleteme,pombredanne/go-deleteme,gnanderson/go,gnanderson/go,dsriram/golang,pombredanne/go-deleteme,tv42/old-go,apparentlymart/golang