RFA: ia64 portion of libunwind patch

[Andrew Cagney]

> Because it may not have the elf binary (at least not locally), and it 
>> may not have debug info.  People still expect GDB to do something 
>> reasonable in those cases.
> 
> 
> I'm a little bit puzzled about why we wouldn't have the elf binary...
> 
> But, assuming for the moment that we do, we'll definitely have the
> unwind info since it's mandated by the ABI.

"at least not locally".  The unwind info can always be found in the 
target's memory.

There are two choices here:
- make the interface more remote friendly
- just ignore the issue until someone complains

Hmm, a good question to ask is "how cross debug friendly" is libunwind.? 
If its anything like libthread-db then this discussion is mute.

Andrew