[emacs] Use c-mode-common-hook, derive from "gnu"

[artagnon]

Summary

Make it clear that the "llvm.org" style is deriving from "gnu" style,
and use the c-mode-common-hook instead of c-mode-hook and c++-mode-hook.

[artagnon]

Ping.

This should be really easy to review and get out of the way; it's borderline non-functional.

[• rafael]

LGTM.

utils/emacs/emacs.el

 ;; LLVM coding style guidelines in emacs
 ;; Maintainer: LLVM Team, http://llvm.org/
 
-;; Add a cc-mode style for editing LLVM C++ code
+;; Add a cc-mode style for editing LLVM C and C++ code
 (c-add-style "llvm.org"
-             '((fill-column . 80)
+             '("gnu"
+         (fill-column . 80)
          (c++-indent-level . 2)
          (c-basic-offset . 2)
          (indent-tabs-mode . nil)
          (c-offsets-alist . ((arglist-intro . ++)
            (innamespace . 0)
-           (member-init-intro . ++)
-           ))
-               ))
+           (member-init-intro . ++)))))
 
 ;; Files with "llvm" in their names will automatically be set to the
 ;; llvm.org coding style.
-(add-hook 'c-mode-hook
+(add-hook 'c-mode-common-hook
     (function
      (lambda nil 
        (if (string-match "llvm" buffer-file-name)
      (progn
-       (c-set-style "llvm.org")
-       )
-         ))))
-
-(add-hook 'c++-mode-hook
-    (function
-     (lambda nil 
-       (if (string-match "llvm" buffer-file-name)
-     (progn
-       (c-set-style "llvm.org")
-       )
-         ))))
+       (c-set-style "llvm.org"))))))