[PATCH] Fix runtime/itrace.c to call arch_has_*_step() prior to calling utrace_control

[Frank Ch. Eigler]

Maynard Johnson <maynardj@us.ibm.com> writes:

> As Roland pointed out in his Mar 31 reply to a posting of mine
> (subject: Re: Testing insn.block probe point uncovers possible
> utrace bug), utrace_control() documents that the caller must ensure
> that arch_has_single_step and arch_has_block_step are defined before
> trying to use those step modes.  [...]

It may be better to put these tests into the translator-emitted
itrace_derived_probe_group::emit_module_init fn or nearby, so we get
registration-time diagnostics (and so utrace/itrace logic for them is
not even attempted).

- FChE