go/parser: consume auto-inserted semi when calling ParseExpr()
go/parser: consume auto-inserted semi when calling ParseExpr()

Fixes issue 1170.

R=rsc
CC=golang-dev
http://codereview.appspot.com/2622041

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