Double buffering is set by default:

SDL_GL_SetAttribute( SDL_GL_DOUBLEBUFFER, 1 );

What you are probably looking for is vsync, that one is disabled:

SDL_GL_SetAttribute( SDL_GL_SWAP_CONTROL, 0 );

But can probably be forced in garphics control panel.

Is there a reason Vsync can't be toggled in the config file?

since there is a patch for it, search here and the answer might already be given

I'm unfamiliar with compiling stuff and am curious about why the option isn't exposed to the user in official releases. I did have a look at a pre-compiled clean SVN version and saw the option was also not present there.

Again, it probably was discussed before and if you search you might find that discussion.

Quick questoin: Why does the forum not send me email notifications of new replies to subscribed threads?

A hicchup perhaps. I didn't get an email myself at first. Now I did. Or your isp filters them as spam?