fix ia64 longjmp() to work from alternate signal-stack

[Ulrich Drepper]

David Mosberger wrote:

> So you want me to create an ia64-specific version of __libc_longjmp()
> which will be sigaltstack-safe while everything else goes to
> the old longjmp implementation, right?

Basically, yes.  Not sure we should keep the name, though.  And even for
other archs, we might have to reset the stack.  Even though the current
code might everywhere in the moment does not mean it is correct.

-- 
➧ Ulrich Drepper ➧ Red Hat, Inc. ➧ 444 Castro St ➧ Mountain View, CA ❖