bug#42210: Add -other-window variants of project-prefix-map commands

[Juri Linkov]

>>>> Would it be possible to define the 'C-x 4 p' map the same way as
>>>> 'C-x p p' is defined?  There is a patch in 
>>>> https://debbugs.gnu.org/41890#127
>>>> to use the default project keymap 'C-x p' in 'C-x p p'.  You could try to
>>>> use the same keymap in 'C-x 4 p', and wrap the command call with
>>>> display-buffer-override-next-command.
>
> I'm not completely clear on the changes you're planning to C-x 4 -- do
> they interact with my proposal, such that I should wait to reroll my
> patch, or can I go ahead and try something equivalent to the patch in
> #41890 you linked to?

While it's still unclear whether the global keymap ‘C-x 4’ will be replaced
by a command, if you want, feel free to try implementing the same to a more
localized keymap ‘C-x 4 p’ based on patches in bug#41890 and on the ELPA
package ‘other-frame-window’.