benchmark

CycleClock: Add support for Alpha architecture (#1753)

* Add support for Alpha architecture

As documented, the real cycle counter is unsafe to use here, because it
is a 32-bit integer which wraps every ~4s.  Use gettimeofday instead,
which has a limitation of a low-precision real-time-clock (~1ms), but no
wrapping.  Passes test suite.

Support parsing /proc/cpuinfo on Alpha

tabular_test: add a missing DoNotOptimize call