pv: adjust application source code for Qt6 support Prepare application source code (C++ programming language files) for Qt6 compatibility. Implement alternative code paths where the API has changed compared to Qt5. This unbreaks Mac OSX 12 builds with homebrew. This change is based on work that was submitted by Dominik Sliwa <redacted>.
Settings: Fix the default item in the language combobox If the language is not set, the default language will be English, but the combobox will show "German"(The first item in language combobox) This is because the current_language will set to "" if the language is not set, and it doesn't match the default language "en"