Patch: add systemtap-style marker to _Unwind_DebugHook

[Tom Tromey]

>>>>> "Rainer" == Rainer Orth <ro@CeBiTec.Uni-Bielefeld.DE> writes:

Rainer> This is wrong: Solaris 10+ has <sys/sdt.h> for DTrace, but only defines
Rainer> DTRACE_* there.

Oops, I forgot that this was a compatibility header.

I think I will make it check for the existence of STAP_PROBE2, unless
there is some better plan.  I don't know anything about dtrace and have
no way to test it, so if we want to use the DTRACE_* macro, somebody
will have to help.

Tom