[$] The ORCs are coming

There are a few reasons for wanting the ability to get proper stack tracesout of the kernel, including profiling, tracing, and debugging kernelcrashes. Historically, the kernel's tracebacks have been unreliable for anumber of reasons, most of which have been fixed in recent years. Now itseems likely that the 4.14 kernel will include a new mechanism thatshould put our traceback problems behind us - for now.