Make view mode more similar to `less'.

Make view mode more similar to `less'.
Changed documentation for most commands.
(view-scroll-auto-exit): New variable, replaces view-mode-auto-exit.
(view-mode-auto-exit): Variable deleted.
(view-mode): Doesn't only toggle `view-mode', it also calls
view-mode-enter or view-mode-exit.
(view-buffer, view-buffer-other-window): New argument exit-action.
(view-file, view-file-other-window, view-buffer-other-window)
(view-buffer, view-mode-enter): Changed method used to restore
windows when leaving view mode.
(view-mode-exit): New function.
(view-return-to-alist): New variable.
(view-return-here, view-exit-position): Variables deleted.
(view-remove-frame-by-deleting, view-exit-all-windows-at-exit):
New option variables.
(view-page-size, view-half-page-size): New variables.
(view-scroll-size): Var deleted; replaced by the previous two.
(view-mode-map): Make the bindings inside defvar.
Added new commands and new key bindings.
Added view-mode-exit to `change-major-mode-hook' to always leave
view mode when changing major mode.
(view-file-other-frame,	view-buffer-other-frame): New commands.
(View-leave, View-kill-and-leave, View-exit, View-exit-and-edit)
(View-quit, View-quit-all): new commands for leaving view mode.
(view-exit): Function deleted.
(View-goto-percent, View-scroll-to-buffer-end): New commands.
(view-try-extend-at-buffer-end): New option variable.

(View-scroll-page-forward, View-scroll-page-backward)
(View-scroll-page-forward-set-page-size)
(View-scroll-page-backward-set-page-size, View-scroll-line-forward)
(View-scroll-line-backward, View-scroll-half-page-forward)
(View-scroll-half-page-backward)
(View-revert-buffer-scroll-page-forward): New commands.

(View-scroll-lines-forward, View-scroll-lines-backward)
(View-scroll-lines-forward-set-scroll-size)
(View-scroll-one-more-line): Commands deleted.

(view-scroll-lines, view-end-message, view-page-size-default)
(view-set-half-page-size-default, view-really-at-end)
(view-recenter): New functions.
(view-scroll-size): Variable deleted.

(View-search-regexp-forward, View-search-regexp-backward)
(View-search-last-regexp-forward, View-search-last-regexp-backward)
(view-search): ! and @ are special at beginning of regexp.
(view-search-no-match-lines): New function.