ptrace single-stepping change breaks Wine

[Roland McGrath]

> I'm getting the feeling that the question of whether to step into
> signal handlers is orthogonal to single-stepping; 

No, it's not.  You only ever step into a handler when you ask to.
That's already the interface.

> Platforms which don't implement PTRACE_SINGLESTEP would probably
> appreciate this.  A "single step" which stops you after setting up the
> signal trampoline and adjusting the PC, before executing any
> instructions in the handler.

That's what PTRACE_SINGLESTEP with a nonzero signal number does since it
was fixed.