CPU (Linux): adds SPARC support

[shalseth]

Summary

/proc/cpuinfo on SPARC has no model name, model, cpu model, hardware or processor
field, so the CPU module prints Unknown. The chip name is in the cpu field, and the clock
frequency is in Cpu<n>ClkTck — in Hz rather than MHz, and in hex on sparc64. SPARC has no
cpufreq sysfs, so that field is the only frequency source.

  # UltraSPARC T4-1 (sun4v)
- CPU: Unknown (64)
+ CPU: UltraSparc T4 (Niagara4) (64) @ 2.85 GHz

  # Sun Fire V240 (sun4u)
- CPU: Unknown (2)
+ CPU: TI UltraSparc IIIi (Jalapeno) (2) @ 1.50 GHz

Related issue

/proc/cpuinfo for both machines is in #1529.

Changes

• parseCpuInfo(): under __sparc__, read the name from cpu and the clock tick from Cpu0ClkTck.
• detectCPUOthers(): convert that from Hz to MHz. sparc64 prints it as %016lx and sparc32 as
  %ld; since a 32-bit userland can run on a 64-bit kernel, the base comes from the value's width
  rather than from the build's bitness.

Core counts already work and are unchanged (8/64 on the T4-1, 2/2 on the V240). sparc32 is untested.

Checklist

• I have tested my changes locally.

[CarterLi]

You should add a new entry UNRELEASED in CHANGELOG since 2.68.1 has been released.

Other changes LGTM.

[shalseth]

Thanks, CHANGELOG updated.