doc/go1.3.html: mention cgo [0]byte bug fix fallout
doc/go1.3.html: mention cgo [0]byte bug fix fallout

Fixes issue 7958.

LGTM=r
R=r
CC=golang-codereviews
https://codereview.appspot.com/91590044

h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang