Applied mainline commit 631a8e4: Move video blit to seperate thread.

src/vid_tandy.c

@@ -237,6 +237,7 @@ void tandy_poll(void *p)
                         if (tandy->displine < tandy->firstline)
                         {
                                 tandy->firstline = tandy->displine;
+                                video_wait_for_buffer();
 //                                printf("Firstline %i\n",firstline);
                         }
                         tandy->lastline = tandy->displine;