Enable kernel-style events (tracepoint) for Litmus. Litmus events
trace the same functions as the sched_trace_XXX(), but can be
enabled independently.

So, why another tracing infrastructure then:
- Litmus tracepoints can be recorded and analyzed together (single
  time reference) with all other kernel tracing events (e.g.,
  sched:sched_switch, etc.). It's easier to correlate the effects
  of kernel events on litmus tasks.

- It enables a quick way to visualize and process schedule traces
  using trace-cmd utility and kernelshark visualizer.
  Kernelshark lacks unit-trace's schedule-correctness checks, but
  it enables a fast view of schedule traces and it has several
  filtering options (for all kernel events, not only Litmus').

Increment a processor-local counter whenever an interrupt is handled.
This allows Feather-Trace to include a (truncated) counter and a flag
to report interference from interrupts. This could be used to filter
samples that were disturbed by interrupts.

User a 32-bit word for all non-preemptive section flags.
Set the "please yield soon" flag atomically when
accessing it on remotely-scheduled tasks.

The macro lock conflicts with locking protocols...

This is useful for measuring locking-related overheads
that are partially recorded in userspace.

This allows us to splice in information into logs from events
that were recorded in userspace.

Instead of doing the hackisch 'write commands to device' thing,
let's  just use a real ioctl() interface.