PPC: return failure from the unw_get_proc_info() stub

Stop pretending that unw_get_proc_info() works on PPC, and instead give
an error back to the caller. As far as I can tell, none of the libunwind
tests clear out the `unw_proc_info_t' before passing it to
unw_get_proc_info(), so they would end up working on garbage data.
1 file changed