Make defvar affect the default binding outside of any let.

* src/eval.c (default_toplevel_binding): New function.
(Fdefvar): Use it.
(unbind_to, backtrace_eval_unrewind): Do a bit of CSE simplification.
(Fdefault_toplevel_value, Fset_default_toplevel_value): New subrs.
(syms_of_eval): Export them.
* src/data.c (Fdefault_value): Micro cleanup.
* src/term.c (init_tty): Use "false".
* lisp/custom.el (custom-initialize-default, custom-initialize-set)
(custom-initialize-reset, custom-initialize-changed): Affect the
toplevel-default-value (bug#6275, bug#14586).
* lisp/emacs-lisp/advice.el (ad-compile-function): Undo previous workaround
for bug#6275.
* test/automated/core-elisp-tests.el: New file.

test/ChangeLog

@@ -1,3 +1,7 @@
+2013-08-02  Stefan Monnier  <monnier@iro.umontreal.ca>
+
+	* automated/core-elisp-tests.el: New file.
+
 2013-08-01  Glenn Morris  <rgm@gnu.org>
 
 	* automated/file-notify-tests.el (file-notify--test-remote-enabled):

test/automated/core-elisp-tests.el

@@ -0,0 +1,38 @@
+;;; core-elisp-tests.el --- Testing some core Elisp rules
+
+;; Copyright (C) 2013 Free Software Foundation, Inc.
+
+;; Author: Stefan Monnier <monnier@iro.umontreal.ca>
+;; Keywords:
+
+;; This program is free software; you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; This program is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;;
+
+;;; Code:
+
+(ert-deftest core-elisp-tests ()
+  "Test some core Elisp rules."
+  (with-temp-buffer
+    ;; Check that when defvar is run within a let-binding, the toplevel default
+    ;; is properly initialized.
+    (should (equal (list (let ((c-e-x 1)) (defvar c-e-x 2) c-e-x) c-e-x)
+                   '(1 2)))
+    (should (equal (list (let ((c-e-x 1)) (defcustom c-e-x 2) c-e-x) c-e-x)
+                   '(1 2)))))
+
+(provide 'core-elisp-tests)
+;;; core-elisp-tests.el ends here