No longer include timestamp in header of .elc files

This removes needless differences between files compiled at different
times or by different people, or from sources in different locations.
Ref: http://lists.gnu.org/archive/html/emacs-devel/2013-03/msg00187.html

* lisp/emacs-lisp/bytecomp.el (byte-compile-insert-header):
No longer include timestamp etc information.

* etc/NEWS: Mention this.

etc/NEWS

@@ -75,6 +75,8 @@ Available only on X, this option allows to control over-scrolling
 using the scroll bar (i.e. dragging the thumb down even when the end
 of the buffer is visible).
 
+** In compiled Lisp files, the header no longer includes a timestamp.
+
 
 * Editing Changes in Emacs 24.4
 

lisp/ChangeLog

@@ -1,3 +1,8 @@
+2013-04-20  Glenn Morris  <rgm@gnu.org>
+
+	* emacs-lisp/bytecomp.el (byte-compile-insert-header):
+	No longer include timestamp etc information.
+
 2013-04-20  Roland Winkler  <winkler@gnu.org>
 
 	* faces.el (read-face-name): Bug fix, return just one face if arg

lisp/emacs-lisp/bytecomp.el

@@ -1997,11 +1997,7 @@ Call from the source buffer."
       ;; >4	byte		x		version %d
       (insert
        ";ELC" 23 "\000\000\000\n"
-       ";;; Compiled by "
+       ";;; Compiled\n"
-       (or (and (boundp 'user-mail-address) user-mail-address)
-	   (concat (user-login-name) "@" (system-name)))
-       " on " (current-time-string) "\n"
-       ";;; from file " filename "\n"
        ";;; in Emacs version " emacs-version "\n"
        ";;; with"
        (cond