syscall: document that documentation is platform specific
syscall: document that documentation is platform specific

Fixes issue 4051

R=golang-dev, minux.ma, rsc
CC=golang-dev
https://codereview.appspot.com/6943063

Committer: Shenghou Ma <b563c57947dc20eb81988e3e3c22786764c14ca8@gmail.com>

rdp/rogerpack2005-golang,glycerine/jeaten-go-arrayof-structof,glycerine/jeaten-go-arrayof-structof,sanjosh/sanjos100-tipc,d0f/go-zh,mhennings/marcohennings-go,scirelli/scirelli-go,webfd/go-zh,scirelli/scirelli-go,glycerine/jeaten-go-arrayof-structof,d0f/go-zh,bryanxu/go-zh,scirelli/scirelli-go,bryanxu/go-zh,rdp/rogerpack2005-golang,rdp/rogerpack2005-golang,sanjosh/sanjos100-tipc,webfd/go-zh,bryanxu/go-zh,d0f/go-zh,rdp/rogerpack2005-golang,mhennings/marcohennings-go,sanjosh/sanjos100-tipc,sanjosh/sanjos100-tipc,webfd/go-zh,mhennings/marcohennings-go,sanjosh/sanjos100-tipc,mhennings/marcohennings-go,mhennings/marcohennings-go,sanjosh/sanjos100-tipc,d0f/go-zh,glycerine/jeaten-go-arrayof-structof,scirelli/scirelli-go,mhennings/marcohennings-go,d0f/go-zh,scirelli/scirelli-go,mhennings/marcohennings-go,scirelli/scirelli-go,sanjosh/sanjos100-tipc,webfd/go-zh,d0f/go-zh,glycerine/jeaten-go-arrayof-structof,webfd/go-zh,rdp/rogerpack2005-golang,webfd/go-zh,glycerine/jeaten-go-arrayof-structof,rdp/rogerpack2005-golang,webfd/go-zh,bryanxu/go-zh,rdp/rogerpack2005-golang,mhennings/marcohennings-go,bryanxu/go-zh,d0f/go-zh,rdp/rogerpack2005-golang,glycerine/jeaten-go-arrayof-structof,webfd/go-zh,scirelli/scirelli-go,bryanxu/go-zh,bryanxu/go-zh,sanjosh/sanjos100-tipc,scirelli/scirelli-go,d0f/go-zh,bryanxu/go-zh,glycerine/jeaten-go-arrayof-structof