Add -other-{window,frame} variants of project-prefix-map commands

[Sean Whitton <spwhitton@spwhitton.name>]

Hello,

It seems like it would be a good idea to have

C-x 4 p f
be like
C-x 4 4 C-x p f

C-x 5 p e
be like
C-x 5 5 C-x p e

etc., since many of the commands in project-prefix-map involve switching
to another buffer.  Certainly project-switch-project, project-find-file
and project-switch-to-buffer would be wanted.

Rather than add definitions of project-find-file-other-window,
project-eshell-other-frame etc., maybe
`display-buffer-override-next-command' could be used so that pressing
C-x 4 p really is just like pressing C-x 4 4 C-x p.

The only disadvantage I can see is that commands like C-x 4 p k would
also be bound and those don't really make sense.

What would be the cleanest way to try to do this?

Thanks.

-- 
Sean Whitton