bug#69566: Context menu for project

[Juri Linkov]

>>> +  (define-key-after menu [project-menu] (bound-and-true-p
>>> project-menu-entry))
>> This variable will probably always be bound (and likely non-nil), given
>> than mouse.el is never distributed separately or used with older versions
>> of Emacs.
>
> Ah, I guess you might be handling the case when project is not loaded
> yet. Perhaps we should autoload something, so that its commands are in the
> context menu anyway?
>
> You could even copy the variable's definition to mouse.el, if that's easier.

Copying it to mouse.el or menu-bar.el makes sense since it will remove
another 'bound-and-true-p' from 'menu-bar-project-menu':

  (defvar project-menu-entry
    `(menu-item "Project" ,(bound-and-true-p menu-bar-project-menu)))

Both mouse.el and menu-bar.el are preloaded.

But the problem is that by its name prefix 'project-'
it belongs to project.el.  Or maybe rename it to
'menu-bar-project-entry'?