bug#1672: we should add an emacs/.dir-locals.el

[Dan Nicolaescu]

Given that we want .dir-locals.el to become widely used, we should lead
by example and add such a file to the distribution.

Here's an example:

((nil . ((indent-tabs-mode . t)
         (tab-width . 8)
         (fill-column . 80)))
 (c-mode . ((c-file-style . "GNU")))
 (change-log-mode . ((add-log-time-zone-rule . t)))
 ("lisp/mail/pmail*"
  . ((nil . ((change-log-default-name . "ChangeLog.pmail"))))))


Some of the things it sets are the default, but some people might change
them in their .emacs, so make sure the right values are used in the
emacs tree.  Another change is to make sure pmail* uses the right
ChangeLog file.