bug#29321: Isearch hit count

[Drew Adams]

> > Isearch could show in the mode line how many matches follow or precede
> > the currently highlighted one (or we could write "3 of 4 matches", as,
> > e.g., Firefox does).  For big files, it could be helpful to calculate
> > this information either lazily or in another thread.
> 
> Thanks to Drew, 

Thanks to you, not me.  I did something similar, but partial
and misguided, trying to use only *-max-*.  The code you
added is similar but DTRT.


> now we have the full-buffer lazy-highlighting
> loop that can be reused for Isearch hit count.
> 
> Here is a minimal patch that implements this feature: