Update documentation of '.dir-locals-2.el'

See https://lists.gnu.org/r/emacs-devel/2017-11/msg00649.html
for more details.
* lisp/files.el (dir-locals-file-2): Remove unused constant.
* lisp/files.el (dir-locals-file): Mention ".dir-locals-2.el" in
the doc string.
* doc/lispref/variables.texi (Directory Local Variables): Mention
".dir-locals-2.el".
* etc/NEWS: Replace `dir-locals-file-2' mention with
`dir-locals-file'.

1 files changed, 1 insertions, 1 deletions

diff --git a/etc/NEWS b/etc/NEWS
index f7a9feb6e49..4ccf468693c 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -366,7 +366,7 @@ These local variables will thus not vanish on setting a major mode.
 
 +++
 ** A second dir-local file (.dir-locals-2.el) is now accepted.
-See the variable 'dir-locals-file-2' for more information.
+See the doc string of 'dir-locals-file' for more information.
 
 +++
 ** Connection-local variables can be used to specify local variables