Doc fixes.

Doc fixes.
(browse-url): Apply, don't just call, browse-url-choose-browser, so
args works properly.
(browse-url-maybe-new-window): New function.
(browse-url-netscape, browse-url-mosaic, browse-url-cci,
browse-url-w3, browse-url-lynx-emacs, browse-url-mail): Use it.
(browse-url-lynx-emacs): Don't call term-term-name.
(browse-url-lynx-input-field, browse-url-lynx-input-delay,
browse-url-lynx-input-attempts): New variables.
(browse-url-lynx-emacs): Use any existing Lynx buffer; take care to
move off input fields.  (After Vladimir Alexiev
<vladimir@cs.ualberta.ca>.)
(browse-url-mosaic-program): New variable.
(browse-url-mosaic): Use browse-url-mosaic-program and
browse-url-new-window-p.
(browse-url-at-mouse): Use browse-url-new-window-p.