bug#8686: 24.0.50; `re-search-backward' does not respect `search-invisible'

[Drew Adams]

> >> The same idea can be used with syntax-ppss to skip over 
> >> matches that are inside comments/strings.
> 
> > Yes, but why not have this built into the search functions 
> > themselves, just as is done for isearch?
> 
> Because I'd rather that the low-level functions do one thing and one
> thing well.

Sure.  Define `re-search-forward' & compagnie in Lisp.
Have them call C functions that each do one simple thing well.

That way, existing code that uses these long-standing functions can benefit from
this feature (or can ignore it) just by binding a variable.