Fix issue with true/false enum if C standard >= C23

[bartgol]

Description

If the compiler supports C23 standard (e.g., gcc 15.2), false and true are reserved keywords, so we need to guard against this line of code.

• Closes Compilation error in timing lib with recent compiler #4902

Checklist

• My code follows the style guidlines of this proejct (black formatting)
• I have performed a self-review of my own code
• My changes generate no new warnings
• I have added tests that excerise my feature/fix and existing tests continue to pass
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding additions and changes to the documentation

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 31.44%. Comparing base (82493b1) to head (b91c796).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #4903   +/-   ##
=======================================
  Coverage   31.44%   31.44%           
=======================================
  Files         264      264           
  Lines       38703    38703           
  Branches     8390     8390           
=======================================
  Hits        12172    12172           
  Misses      25291    25291           
  Partials     1240     1240           

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