Backward compatibility for insn probe point

[Roland McGrath]

> Off the top of my head that might mean there is a specific ppc64 utrace
> problem.
> 
> Roland, do you know of any problems with original utrace doing
> UTRACE_ACTION_SINGLESTEP on ppc64?

Sorry, I can't remember anything in particular.  There might well have been
some issue that I've forgotten.


Thanks,
Roland