Add .dir-locals.el.

Add .dir-locals.el.

* .dir-locals.el: New file, to help Emacs users produce better
  changesets.  In particular, prevents automatic copyright year
  updates.

BUG=

Committed: http://code.google.com/p/v8/source/detail?r=13884

[wingo, 2013-03-08 10:48:12]

Good idea or bad idea?

[Sven Panne, 2013-03-08 13:45:27]

LGTM, I hope this won't clash somehow with our arcane local emacs
infrastructure. %-}

[Sven Panne, 2013-03-08 13:48:03]

Committed patchset #1 manually as r13884 (presubmit successful).