bug#33033: 27.0.50; [wishlist] Registers for non-file buffers

[Helmut Eller]

1.) It would be nice if the register machinery could also be used for
switching to buffers that aren't connected to a file but have
more-or-less fixed names like *shell*, *Backtrace*, or *scratch*.

E.g. (set-register ?s '(buffer "*scratch*")) could set up things so that
C-x r j s would switch to the *scratch* buffer.

2.) Similarly, it would be useful to have a way to switch to a buffer
based on the buffer's mode.

E.g. (set-register ?l '(mode emacs-lisp)) could switch to the last
recently used buffer in emacs-lisp mode.

I suppose I could implement this myself with registerv-make, but maybe
those two use cases should be standardized and documented.

Helmut