Fix devIocStats by including posix headers

[AlexanderWells-diamond]

This relies on the config_var "POSIX" being defined as True/False for the current platform.

The test is pretty simple, just the CPU count and IOC CPU load as they're fairly easy to calculate

Fixes #131

[github-actions[bot]]

Unit Test Results

     15 files  ±  0       15 suites  ±0   29m 33s :stopwatch: +58s    273 tests +  1     257 :heavy_check_mark: +  1    16 :zzz: ±0  0 :x: ±0  4 095 runs  +15  3 505 :heavy_check_mark: +15  590 :zzz: ±0  0 :x: ±0 

Results for commit 40dfcfa9. ± Comparison against base commit 289897ee.

:recycle: This comment has been updated with latest results.

[codecov[bot]]

Codecov Report

Merging #134 (40dfcfa) into master (289897e) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #134   +/-   ##
=======================================
  Coverage   87.44%   87.44%           
=======================================
  Files          14       14           
  Lines         996      996           
=======================================
  Hits          871      871           
  Misses        125      125