doc/go1.4: mention that we are going to need a new version of SWIG
doc/go1.4: mention that we are going to need a new version of SWIG

Update issue 8750

CC=golang-codereviews
https://codereview.appspot.com/153950044

d0f/go-zh,d0f/go-zh,sanjosh/sanjos100-tipc,sanjosh/sanjos100-tipc,d0f/go-zh,bryanxu/go-zh,bryanxu/go-zh,bryanxu/go-zh,bryanxu/go-zh,webfd/go-zh,sanjosh/sanjos100-tipc,webfd/go-zh,webfd/go-zh,sanjosh/sanjos100-tipc,webfd/go-zh,sanjosh/sanjos100-tipc,bryanxu/go-zh,d0f/go-zh,bryanxu/go-zh,webfd/go-zh,d0f/go-zh,d0f/go-zh,webfd/go-zh,sanjosh/sanjos100-tipc,sanjosh/sanjos100-tipc,bryanxu/go-zh,bryanxu/go-zh,d0f/go-zh,sanjosh/sanjos100-tipc,webfd/go-zh,webfd/go-zh,d0f/go-zh