Bring opengles up-to-date with nightly 

Hey, I use these bindings of openGL for [my own project](https://github.com/bollu/spy/tree/dev). However, these don't seem to be up-to-date and weren't compiling. I fixed the compiler errors, so I decided to make a pull request out of it. The errors were that of the deprecated ```*T``` syntax. Has to be ```*const T``` now.

I'm guessing this won't be merged into ```mozilla-servo:master``` since I think servo tracks an older verison of Rust. I could change the target branch or some such.

I felt it would be useful to anyone else trying to use these bindings. Thanks!