Update source to SDL2 2.0.12

Edward Rudd

2020-05-02 03f8528315fa46c95991a34f3325d7b33ae5538c

 source/visualtest/unittest/testquit.c

@@ -64,7 +64,8 @@

        if(consumed < 0)
        {
            SDLTest_Log("Usage: %s %s [--exit-code N] [--crash] [--hang]", argv[0], SDLTest_CommonUsage(state));
            static const char *options = { "[--exit-code N]", "[--crash]", "[--hang]", NULL };
            SDLTest_CommonLogUsage(state, argv[0], options);
            SDLTest_CommonQuit(state);
            return 1;
        }