Fix boost compiler warnings

Work around an issue in boost. https://github.com/boostorg/property_tree/pull/50

added BugFix label

requested review from @v.friese

approved this merge request

Dear @f.uhlig, @v.friese, @p.-a.loizeau,

you have been identified as code owner of at least one file which was changed with this merge request.

Please check the changes and approve them or request changes.

added CodeOwners label

added 7 commits

• 2bf098d0...cf769402 - 6 commits from branch computing:master
• 80509000 - Fix boost compiler warnings

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merged