Switched the Quasi88 upstream repository to the "Quasi88Kai" fork [1], since it has some new developments and also supports SDL2.
Changes in the fork:
* General updates to the build system and migration to CMake
* All files converted to UTF-8
* Many improvements in Windows, X11, GTK and SDL backends
* Add a RetroAchievements-compatible version "RAQUASI88" (only for Windows at this time)
Had to apply a build patch since:
* SDL2 2.0.10 libraries do not provide the SDL:SDL aliases in the `sdl2-config.cmake`
* Buster's GCC (8) is implementing the filesystem C++17 API in `libstdc++fs`
[1] https://github.com/winterheart/quasi88
* change existing calls which used --strip-components
* use multiple parameters for arguments which should allow additional arguments with spaces
* implements #2630
* replace many of the existing wget | tar commands with the new function
* include error logging in the function via runCmd, to trap download/unpacking issues
