Tell SDL to notfree my video surfaces (Damn, no how-to write a SDL driver)

--HG--
extra : convert_revision : svn%3Ac70aab31-4412-0410-b14c-859654838e24/trunk%401104

src/video/gem/SDL_gemvideo.c

@@ -696,7 +696,7 @@ SDL_Surface *GEM_SetVideoMode(_THIS, SDL_Surface *current,
 	}
 
 	/*--- Initialize screen ---*/
-	modeflags = 0;
+	modeflags = SDL_PREALLOC;
 	if (VDI_bpp == 8) {
 		modeflags |= SDL_HWPALETTE;
 	}

src/video/xbios/SDL_xbios.c

@@ -529,7 +529,7 @@ static SDL_Surface *XBIOS_SetVideoMode(_THIS, SDL_Surface *current,
 		return(NULL);
 	}
 
-	modeflags = SDL_FULLSCREEN;
+	modeflags = SDL_FULLSCREEN | SDL_PREALLOC;
 
 	/* Allocate needed buffers: simple/double buffer and shadow surface */
 	new_video_mode = XBIOS_videomodes[bpp][mode];