[PATCH] Report dlsym, dlvsym lookup errors using dlerror [BZ #19509]

[Florian Weimer]

* Carlos O'Donell:

> A POSIX clarification should probably be made here, but I agree
> that from a QoI it is better to return some kind of error because
> that's users expect. I also expect that's what other implementations
> do (but haven't verified).

It's also what the Solaris examples suggest:

  <http://docs.oracle.com/cd/E19683-01/816-1386/chapter3-26/index.html>

I don't see any reason why RTLD_NEXT should behave differently from
other handles.