shave size by removing exceptions support

[anholt]

Noticed while looking at someone else's CFLAGS, might be particularly promising for us:

https://www.chromium.org/chromium-os/build/c-exception-support

[nwnk]

I think that would break passing a callback to glDebugMessageCallbackARB if said passed function (called C++ code that) threw an exception.

[anholt]

Yeah, I had that thought too, but that seemed like a reasonable tradeoff.