Fix minor errors on Apple

[timmah]

Background

• Found two minor bugs on Mac builds that result in compilation errors

Purpose of Pull Request

• Fix those bugs

Description of changes

• In c4/xthi_cpuset.hh, comment out parameters that are not used in the Apple implementation of sched_getaffinity.
• In cdi_analytic/test/tstCompound_Analytic_MultigroupOpacity.cc, rename sig_t to sig_test, since the former conflicts with a typedef in Apple's sys/signal.h.

Status

• Reference:
  • Pre-Merge Code Review
  • CDash Status
• Checks
  • Travis/Appveyor CI checks pass
  • Code coverage does not decrease
  • Valgrind test passes
  • Toss3 checks pass
  • Trinitite checks pass
  • Code reviewed/approved, sufficient DbC checks, testing, documentation

[codecov]

Codecov Report

Merging #789 into develop will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           develop    #789   +/-   ##
=======================================
  Coverage       94%     94%           
=======================================
  Files          367     367           
  Lines        17229   17229           
=======================================
  Hits         16197   16197           
  Misses        1032    1032

[KineticTheory]

BTW - nice timing on this PR. It tested changes I made to the regression environment. The snow testing ran with cmake/3.17.0 (related to #788).

[KineticTheory]

I marked tests as passing. The reported failures are unrelated to this PR (see #788). We don't have CI that will actually process the first change you made. As long as the code compiles on one machine, I think we are good.