goplay: fix to run under windows.
goplay: fix to run under windows.

Fixes issue 1204.

R=golang-dev, brainman, Joe Poirier, alex.brainman, adg
CC=golang-dev, math-nuts
http://codereview.appspot.com/2532041

Committer: Andrew Gerrand <395a7d33bec8475c9b83b7d440f141bcbd994aa5@golang.org>

tav/go,tav/go,tav/go,tav/go,tav/go,tav/go,tav/go