This was done with this script:

    #!/bin/bash

    set -eou pipefail

    # Use C++11 sstream constructor from string
    # Exclude 'ThirdParty' because it uses ossimFilename type
    find Modules/ Examples/ -not -iwholename "*ThirdParty*" -type f -print0 | xargs -0 sed -i -E "s/std::ifstream (.*)\((.*)\.c_str\(\)/std::ifstream \1\(\2/"
    find Modules/ Examples/ -not -iwholename "*ThirdParty*" -type f -print0 | xargs -0 sed -i -E "s/std::ofstream (.*)\((.*)\.c_str\(\)/std::ofstream \1\(\2/"

    # Use C++11 ::open(const std::string&) of ifstream, ofstream, etc.
    # Exclude ThirdParty because of ossimFilename type
    find Modules/ Examples/ -not -iwholename "*ThirdParty*" -type f -print0 | xargs -0 sed -i -E "s/\.open\((.*).c_str\(\)/\.open\(\1/"

    # No need for c_str when outputing to std::cout and such
    find Modules/ Examples/ -type f -print0 | xargs -0 sed -i -E "s/\.c_str\(\) ?<</ <</"

    # Use itk::ExceptionObject::SetDescription and SetLocation string versions
    find Modules/ Examples/ -type f -print0 | xargs -0 sed -i -E "s/e\.SetDescription\((.*)\.c_str\(\)\)/e\.SetDescription\(\1\)/"
    find Modules/ Examples/ -type f -print0 | xargs -0 sed -i -E "s/e\.SetLocation\((.*)\.c_str\(\)\)/e\.SetLocation\(\1\)/"

    # Use itksys::SystemTool:: string versions
    find Modules/ Examples/ -type f -print0 | xargs -0 sed -i -E "s/itksys::SystemTools::(.*)\((.*)\.c_str\(\)/itksys::SystemTools::\1\(\2/"
    # Exclude otbLogger because it uses GetCurrentDateTime which does not have a string version
    git checkout --  Modules/Core/Common/src/otbLogger.cxx
    # Exclude test/otbOGRLayerStreamStitchingFilter.cxx because there's a double use which is not compatible with the regex
    git checkout -- Modules/Segmentation/OGRProcessing/test/otbOGRLayerStreamStitchingFilter.cxx