RFA: ia64 patch required after recent osabi changes

[Andrew Cagney]

> Patch checked in.  This fixes the regression with the new osabi code and ia64 signal handling backtrace without having to remove the assertion.

Nice.  So everyone's clear, the assertion is correct and needed.
The function is forcing an architecture switch so if the switch fails 
(what the assertion was checking) GDB's a bit stuffed.


enjoy,
Andrew