[Rd] Links to non-vignette documentation

[hadley wickham]

> No, there's no automatic building after the promptPackage call.  It's up
> to you to decide which functions need to be mentioned to users.  In
> large packages it usually doesn't make sense to list all the functions,
> so the package writer needs to use judgement here.  There are other
> mechanisms (e.g. ls("package:XXX") for a list of names, the help index
> generation for a list of names and titles) to get a list of everything.

Ok, that seems reasonable, but perhaps promptPackage (or
documentation) could make this more clear.

> There aren't any immediate plans to change help(package=XXX), but I
> think in the long run, if package?XXX receives wider support than it has
> now, it would make sense to make that change.

When was this form of package documentation created?  How are users
supposed to know it exists?  I couldn't find any pointers to it from
?help, ?library or from help(package=XXX).

Hadley