os: add a few missing plan9 errors

these were needed by packages in crypto/ and by io/ioutil

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/4350047

diff --git a/src/pkg/os/error_plan9.go b/src/pkg/os/error_plan9.go
index 0f34f04a4de00ca070d4bf93ae75f46efe30a3f0..d6575864e843d4e1f33ab0518a6a003d03970f04 100644 (file)
--- a/src/pkg/os/error_plan9.go
+++ b/src/pkg/os/error_plan9.go
@@ -35,10 +35,14 @@ var (
        Ebadarg    = NewError("bad arg in system call")
        Enotdir    = NewError("not a directory")
        Enonexist  = NewError("file does not exist")
+       Eexist     = NewError("file already exists")
+       Eio        = NewError("i/o error")
 
        EINVAL  = Ebadarg
        ENOTDIR = Enotdir
        ENOENT  = Enonexist
+       EEXIST  = Eexist
+       EIO     = Eio
 
        ENAMETOOLONG = NewError("file name too long")
        ERANGE       = NewError("math result not representable")