constify structures passed as reading parameters

Most of them come from libdvdread and should never be modified.

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• 8d0f467b...253c4376 - 2 commits from branch videolan:master
• 340ae1a0 - constify structures passed as reading parameters

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added 6 commits

• 340ae1a0...e5425979 - 5 commits from branch videolan:master
• cf720818 - constify structures passed as reading parameters

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approved this merge request

merged

changed milestone to %7.0.0