Add a Doc View tool bar

Add a Doc View tool bar

* etc/NEWS: Announce the new tool bar.
* etc/images/last-page.xpm:
* etc/images/last-page.pbm: New images.  Mirrored from
next-page.xpm.
* lisp/doc-view.el (doc-view-menu): Use `doc-view-new-search'
instead of an anonymous function.
(doc-view-tool-bar-map): New keymap.
(doc-view-search): Update the tool bar after initiating a
search.
(doc-view-new-search): New command.
(doc-view-mode): Set the tool bar map appropriately.