flag: fix error in documentation example. Fixes issue 1615. This time for sure.
flag: fix error in documentation example.
Fixes issue 1615.
This time for sure.

R=rsc, gri
CC=golang-dev
http://codereview.appspot.com/4275079

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