misc/emacs: do not highlight built-in function if not followed by '('
misc/emacs: do not highlight built-in function if not followed by '('

Name of built-in function is not reserved word in Go, and you can
use it as variable name. "new" is often used as local variable, for
instance.

This patch is to apply font-lock-builtin-face only when built-in
function name is followed by '(', so that it doesn't highlight
non-function variable that happen to have the same name as built-in
function.

LGTM=dominik.honnef
R=golang-codereviews, dominik.honnef, adonovan
CC=golang-codereviews
https://codereview.appspot.com/79260043

Committer: Alan Donovan <7069e9552f9d110b0a0f326b96f22f63fb99dfc1@google.com>

rdp/rogerpack2005-golang,bryanxu/go-zh,webfd/go-zh,rdp/rogerpack2005-golang,sanjosh/sanjos100-tipc,rdp/rogerpack2005-golang,rdp/rogerpack2005-golang,d0f/go-zh,rdp/rogerpack2005-golang,bryanxu/go-zh,bryanxu/go-zh,webfd/go-zh,rdp/rogerpack2005-golang,sanjosh/sanjos100-tipc,bryanxu/go-zh,rdp/rogerpack2005-golang,webfd/go-zh,rdp/rogerpack2005-golang,d0f/go-zh,sanjosh/sanjos100-tipc,bryanxu/go-zh,bryanxu/go-zh,d0f/go-zh,webfd/go-zh,bryanxu/go-zh,webfd/go-zh,sanjosh/sanjos100-tipc,webfd/go-zh,sanjosh/sanjos100-tipc,bryanxu/go-zh,d0f/go-zh,d0f/go-zh,sanjosh/sanjos100-tipc,d0f/go-zh,d0f/go-zh,webfd/go-zh,sanjosh/sanjos100-tipc,sanjosh/sanjos100-tipc,d0f/go-zh,webfd/go-zh