[RFC/ia64] link against libunwind rather than using dlopen

[Joel Brobecker]

> Joel> This is something that I mentioned back in Aug 2005, and which came back
> Joel> to bite me a little. Basically, on ia64 hosts, we dlopen libunwind rather
> Joel> that link GDB against it.
> [...]
> Joel> What do you guys think?
> 
> Why do we currently use dlopen?

Hard to answer that question for certain. I had a hunch shortly
after I sent this message, though: On the (relatively old) Linux
machine that we have at AdaCore, I can't link against the system
libunwind. I think it's a linker bug, as the linker is complaining
about missing symbols, whereas I can see them fine.  These are
protected symbols, but they are there. No problem with GNU
libunwind.  But I did send a message to Jan asking him if he could
test on a newer distro, and he said that he'd get back to me
as soon as he has time.

-- 
Joel