browse-url: mark some of the more obsolete stuff as such

browse-url: mark some of the more obsolete stuff as such

* lisp/net/browse-url.el (browse-url-browser-function)
(browse-url-default-browser):
Remove obsolete items from the explicit listing.
(browse-url-new-window-flag, browse-url-of-file-hook): Doc fixes.
(browse-url-netscape-program, browse-url-netscape-arguments)
(browse-url-netscape-startup-arguments)
(browse-url-galeon-program, browse-url-galeon-arguments)
(browse-url-galeon-startup-arguments)
(browse-url-gnome-moz-program, browse-url-gnome-moz-arguments)
(browse-url-galeon-new-window-is-tab)
(browse-url-netscape-new-window-is-tab)
(browse-url-mosaic-program, browse-url-mosaic-arguments)
(browse-url-mosaic-pidfile, browse-url-CCI-port)
(browse-url-CCI-host, browse-url-netscape-version)
(browse-url-netscape, browse-url-netscape-sentinel)
(browse-url-netscape-reload, browse-url-netscape-send)
(browse-url-galeon, browse-url-galeon-sentinel)
(browse-url-gnome-moz, browse-url-mosaic, browse-url-cci)
(browse-url-w3-gnudoit): Make obsolete.

* etc/NEWS: Mention this.

* doc/misc/idlwave.texi (HTML Help Browser Tips): Remove obsolete info.

* lisp/ffap.el (ffap-url-fetcher): Simplify default and doc.

* lisp/x-dnd.el: Comment update.