Default value for SGI swap control GL attribute should be -1.

Explicitly try to set it if you want a different value. Different glX
 implementations appear to have different defaults for this, and you can't
 query them for the current value.

--HG--
branch : SDL-1.2
extra : convert_revision : svn%3Ac70aab31-4412-0410-b14c-859654838e24/branches/SDL-1.2%403998

src/video/x11/SDL_x11video.c

@@ -122,7 +122,7 @@ static SDL_VideoDevice *X11_CreateDevice(int devindex)
 		SDL_memset(device->gl_data, 0, (sizeof *device->gl_data));
 
 #if SDL_VIDEO_OPENGL_GLX
-		device->gl_data->sgi_swap_interval = 1;
+		device->gl_data->sgi_swap_interval = -1;
 #endif
 
 		/* Set the driver flags */