bug#1352: 23.0.60; isearch-success-function

[Drew Adams]

> > The name of `isearch-success-function' seems wrong, if we 
> > believe the doc string. The doc string suggests that it is
> > a predicate that filters the search hits that would
> > otherwise be available. That's very general. If that's true,
> > then the name should reflect this meaning -
> > perhaps `isearch-predicate'.
> 
> Actually, based on your description, I'd name it 
> `isearch-filter-predicate'.

Sound good to me. 

(Although by the "principe des belles oranges", an Isearch predicate could
pretty much only be for filtering.)