misc/emacs: update go-mode syntax table and comment handling as suggested by pkleiweg.
misc/emacs: update go-mode syntax table and comment handling as
suggested by pkleiweg.

Fixes issue 3471.

R=adonovan, pkleiweg, rsc
CC=golang-dev
https://codereview.appspot.com/7060056

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