base-mode.lisp: add emacs bookmark keybindings.
base-mode.lisp: add emacs bookmark keybindings.

These are based on the following vanilla Emacs keybindings:

"C-x r M" 'bookmark-set-no-overwrite
"C-x r b" 'bookmark-jump
"C-x r l" 'bookmark-bmenu-list
"C-x r m" 'bookmark-set

jmercouris/NeXT,jmercouris/NeXT