Bump pFUnit version

[danielhollas]

We've been pinning the pFUnit version to an old commit for GCC 7 support. But we no longer test GCC 7 so let's update to the latest official version. (this is also a pre-requisite for compilation on MacOS, see #219 )

Also fixed shellcheck linter violations in all scripts in dev_scripts directory.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 84.06%. Comparing base (fbbdb89) to head (35f7099).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #238   +/-   ##
=======================================
  Coverage   84.06%   84.06%           
=======================================
  Files          47       47           
  Lines        6613     6613           
  Branches      766      766           
=======================================
  Hits         5559     5559           
  Misses        855      855           
  Partials      199      199           

Flag	Coverage Δ
unittests	18.37% <ø> (ø)

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