Add missing export macros in lexical_casts.hpp

[traversaro]

#1281 made hardware_interface::stod and hardware_interface::parse_bool proper methods defined in the shared library, but the export macros were not properly added there.

• Fork the repository.
• Modify the source; please focus on the specific change you are contributing. If you also reformat all the code, it will be hard for us to focus on your change.
• Ensure local tests pass. (colcon test and pre-commit run (requires you to install pre-commit by pip3 install pre-commit)
• Commit to your fork using clear commit messages.
• Send a pull request, answering any default questions in the pull request interface.
• Pay attention to any automated CI failures reported in the pull request, and stay involved in the conversation.

[bmagyar]

Thank you!

[codecov]

Codecov Report

Attention: 4 lines in your changes are missing coverage. Please review.

Comparison is base (786d5b5) 47.49% compared to head (3c1f9e9) 75.88%.
Report is 6 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff             @@
##           master    #1382       +/-   ##
===========================================
+ Coverage   47.49%   75.88%   +28.38%     
===========================================
  Files          41       41               
  Lines        3556     3359      -197     
  Branches     1938     1935        -3     
===========================================
+ Hits         1689     2549      +860     
+ Misses        459      418       -41     
+ Partials     1408      392     -1016     

Flag	Coverage Δ
unittests	75.88% <20.00%> (+28.38%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
controller_manager/src/controller_manager.cpp	69.43% <20.00%> (+30.66%)	⬆️

... and 31 files with indirect coverage changes

[christophfroehlich]

thx