Instead of QMessageBox::question and QMessageBox::information, use the OBSMessageBox class, which translates all buttons.
This adds close buttons to remux dialog, output timer dialog, and advanced audio properties dialog. I also did a small refactor of the remux dialog so the buttons were consistent with other dialogs. Closes jp9000/obs-studio#876
This is to prevent confusion both when prefixing commits and when reading the directory structure for the first time.