Use the correct (raw) names for hardware-interrupt perf events.

Part of #610.

Something in the libpfm stack stopped understanding the HW_INTERRUPTS event, but that's OK: in meantime, it's grown support for parsing raw perf-event names.  That's fabulous, because it allows us to be 100% sure we're using the same events that are mentioned in the [deterministic counters bible](http://web.eece.maine.edu/~vweaver/projects/deterministic/deterministic_counters.pdf).