(Startup Summary): Add xref to documentation of `initial-window-system'.

doc/lispref/ChangeLog

 2008-12-20  Eli Zaretskii  <eliz@gnu.org>
 
+	* os.texi (Startup Summary): Add xref to documentation of
+	`initial-window-system'.
+
 	* display.texi (Window Systems): Document `window-system' the
 	function.  The variable `window-system' is now frame-local.
+	Document `initial-window-system'.
 
 2008-12-19  Martin Rudalics  <rudalics@gmx.at>
 

doc/lispref/os.texi

@@ -80,7 +80,8 @@ that Emacs initialization is in progress.
 @vindex window-system-initialization-alist
 @item
 It loads the initialization library for the window system specified by
-the variable @code{initial-window-system}.  This library's name is
+the variable @code{initial-window-system} (@pxref{Window Systems,
+initial-window-system}).  This library's name is
 @file{term/@var{windowsystem}-win.el}, where @var{windowsystem} is the
 value of @code{initial-window-system}.  From that library, it calls
 the appropriate initialization function.  The initialization function

etc/NEWS

@@ -1646,6 +1646,7 @@ $TERM inherited by Emacs you will have to look inside initial-environment.
 ---
 *** $DISPLAY is now dynamically inherited from the frame's `display'.
 
++++
 *** The `window-system' variable is now frame-local.  The new
 `initial-window-system' variable contains the `window-system' value
 for the first frame.  `window-system' is also now a function that