Not a user-visible API change. Just a minor garbage
win in contrived cases.
Also, the package is io/ioutil.
R=golang-dev, r
CC=golang-dev
https://golang.org/cl/
12987044
image/draw: added Quantizer type (CL 11148043).
image/gif: added Encode and EncodeAll (CL 10896043).
io: Copy prioritizes WriterTo over ReaderFrom (CL 9462044).
-ioutil: add WriteString to Discard (CL 12580045).
net: new build tag netgo for building a pure Go net package (CL 7100050).
net/http: don't allow sending invalid cookie lines (CL 12204043).
net/http: allow ReadResponse with nil *Request parameter (CL 9821043).