Allow testalpha.c to toggle windowed/fullscreen mode.

This is to help track down bugs in the updated Mac OS X video target.

test/testalpha.c

@@ -505,14 +505,24 @@ fprintf(stderr, "Slept %d ticks\n", (SDL_GetTicks()-ticks));
 					}
 					break;
 				case SDL_KEYDOWN:
-#ifndef _WIN32_WCE
+#ifdef _WIN32_WCE
+					// there is no ESC key at all
+					done = 1;
+#else
 					if ( event.key.keysym.sym == SDLK_ESCAPE ) {
 						done = 1;
+					} else if (event.key.keysym.sym == SDLK_t) {
+						videoflags ^= SDL_FULLSCREEN;
+						screen = SDL_SetVideoMode(w, h, video_bpp, videoflags);
+						if ( screen == NULL ) {
+							fprintf(stderr, "Couldn't toggle video mode: %s\n",
+									SDL_GetError());
+							quit(2);
+						}
+						FillBackground(screen);
 					}
-#else
-					// there is no ESC key at all
-					done = 1;
 #endif
+
 					break;
 				case SDL_QUIT:
 					done = 1;