doc/go1.3.txt: mention windows syscall.NewCallbackCDecl
doc/go1.3.txt: mention windows syscall.NewCallbackCDecl

R=golang-codereviews, r
CC=golang-codereviews
https://codereview.appspot.com/44160044

tv42/old-go,tv42/old-go,tv42/old-go,pombredanne/go-deleteme,tv42/old-go,pombredanne/go-deleteme,pombredanne/go-deleteme,tv42/old-go,pombredanne/go-deleteme,pombredanne/go-deleteme,pombredanne/go-deleteme,tv42/old-go,pombredanne/go-deleteme,tv42/old-go