v3.1.1-rc8

• (Again) hopefully fixing Qt5 linking issues on Ubuntu FOR REAL THIS TIME (@revmischa)
• Monitor stretching support (@milkdropper)
• Use updates synchronized with vertical retrace if adaptive vsync fails (@jas-per)
• Fix OSX install by use of preset subdirs (@AlwinEsch)
• Menus, keys, FPS tracking (@milkdropper)
• Lower default meshX setting for improved performance at some possible loss of quality

iTunes (now Music) plugin on Catalina doesn't work still - we really need to locate some documentation on how to support Music.app - #251