[RFA] Don't use thread_db on corefiles

[Andrew Cagney]

> Hmm, perhaps it is a native GDB looking at a threaded core file?  In 
>> that case, yes the thread-db should drop its self on top.  If that is 
>> causing an internal error then there is something messed up that should 
>> be fixed.
> 
> 
> Yes, that's where the internal error is.  They're based on the fact
> that thread-db tries to enable event reporting, as best I can tell.


Sounds like that is the bug to fix.  Enabling event reporting probably 
doesn't make much sense when the target is lifeless.

enjoy,
Andrew