codereview: accommodate recent change to ui.prompt
codereview: accommodate recent change to ui.prompt

Fixes issue 525.

R=r
CC=golang-dev
http://codereview.appspot.com/190044

pombredanne/go-deleteme,tv42/old-go,ssrl/go,apparentlymart/golang,nightlyone/golang,bdwalton/debian-golang,nightlyone/golang,bdwalton/debian-golang,h8liu/golang,apparentlymart/golang,bdwalton/debian-golang,bdwalton/debian-golang,apparentlymart/golang,h8liu/golang,nightlyone/golang,gnanderson/go,ssrl/go,tv42/old-go,nightlyone/golang,bdwalton/debian-golang,ssrl/go,gnanderson/go,dsriram/golang,tianon/debian-golang,tianon/debian-golang,apparentlymart/golang,pombredanne/go-deleteme,h8liu/golang,h8liu/golang,pombredanne/go-deleteme,dsriram/golang,nightlyone/golang,gnanderson/go,pombredanne/go-deleteme,dsriram/golang,nightlyone/golang,tianon/debian-golang,bdwalton/debian-golang,tv42/old-go,apparentlymart/golang,dsriram/golang,tv42/old-go,h8liu/golang,gnanderson/go,dsriram/golang,ssrl/go,gnanderson/go,gnanderson/go,nightlyone/golang,gnanderson/go,tianon/debian-golang,tianon/debian-golang,pombredanne/go-deleteme,pombredanne/go-deleteme,tv42/old-go,tianon/debian-golang,tv42/old-go,tv42/old-go,dsriram/golang,apparentlymart/golang,h8liu/golang,ssrl/go,tianon/debian-golang,bdwalton/debian-golang,apparentlymart/golang,ssrl/go,bdwalton/debian-golang,h8liu/golang,dsriram/golang,tianon/debian-golang,pombredanne/go-deleteme,ssrl/go