Add sdl_vsync option (vertical sync with SDL_Renderer)

BasiliskII/src/SDL/video_sdl2.cpp

@@ -793,8 +793,15 @@ static SDL_Surface * init_sdl_video(int width, int height, int bpp, Uint32 flags
 #else
 			SDL_SetHint(SDL_HINT_RENDER_DRIVER, "");
 #endif
+	    }
+
+		bool sdl_vsync = PrefsFindBool("sdl_vsync");
+		if (sdl_vsync) {
+			SDL_SetHint(SDL_HINT_RENDER_VSYNC, "1");
 		}
+
 		sdl_renderer = SDL_CreateRenderer(sdl_window, -1, 0);
+
 		if (!sdl_renderer) {
 			shutdown_sdl_video();
 			return NULL;

SheepShaver/src/Windows/prefs_windows.cpp

@@ -56,6 +56,7 @@ prefs_desc platform_prefs_items[] = {
 	{"portfile1", TYPE_STRING, false,               "output file for serial port 1"},
 #ifdef USE_SDL_VIDEO
 	{"sdlrender", TYPE_STRING, false,      "SDL_Renderer driver (\"auto\", \"software\" (may be faster), etc.)"},
+	{"sdl_vsync", TYPE_BOOLEAN, false,     "Make SDL_Renderer vertical sync frames to host (eg. with software renderer)"},
 #endif
 
 	{NULL, TYPE_END, false, NULL} // End of list