test: make bug107 os.Error-proof

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/5306087

test/fixedbugs/bug107.go

@@ -6,7 +6,7 @@
 
 package main
 import os "os"
-type _ os.Error
+type _ os.FileInfo
 func f() (os int) {
 	 // In the next line "os" should refer to the result variable, not
 	 // to the package.