Require Qt 5.9 from now

src/CMakeLists.txt

src/libs/core/score/tmeasureobject.cpp

src/libs/core/score/tnoteobject.cpp

src/libs/core/score/tstaffobject.cpp

src/qml/+android/MainMenuMobile.qml

src/qml/DialogLoader.qml

src/qml/MainMenu.qml

src/qml/MainScore.qml

src/qml/MainWindow.qml

src/qml/NootkaLabel.qml

src/qml/NoteName.qml

src/qml/TtoolBar.qml

src/qml/about/AboutPage.qml

src/qml/about/AuthorsPage.qml

src/qml/about/ChangesPage.qml

src/qml/about/DonorsPage.qml

src/qml/about/HelpPage.qml

src/qml/about/LicensePage.qml

src/qml/about/QtPage.qml

src/qml/about/SupportPage.qml