bug#69542: Feature request: making occur obey isearch-filter-predicate

[Juri Linkov]

>      An alternative would be to add a new variable
> 're-search-forward-function' and then to use it like
> '(funcall re-search-forward-function)'.
>
> The idea of a new function seems good to me.

Indeed, and this will require only a simple change in 'how-many'
and other functions to replace such calls

  (re-search-forward regexp rend t)

with

  (funcall re-search-forward-function regexp rend t)