buffer.lisp: Remove new-buffer-* defun, replace with local commands.
buffer.lisp: Remove new-buffer-* defun, replace with local commands.

We can leverage the new url-designator type to use the same action for
history-entries, bookmarks, etc.

This shortens the code and allows us to define actions in one spot per command,
instead of repeating them for each source.

jmercouris/NeXT,jmercouris/NeXT