bug#10998: Allow movements in bookmark-bmenu-search.

[Stefan Monnier]

>>> there is no cursor in the prompt of bookmark-bmenu-search, and it is not
>>> possible to move and edit it actually, this patch allow this.
>> Couldn't we fix that another way, using a real minibuffer, with an
>> after-change-function to update the set of matching entries?
> I don't know much about after-change-functions, but I guess yes it
> would be possible.  However it will change all the logic of this code
> and need a complete rewrite.

Indeed, but it will make all cursor motion commands work "as usual"
rather than hard-coding C-f, C-b etc...


        Stefan