Description: Enable Cairo GL Backend

Hello, I am asking from you to enable Cairo GL backend.

Why? Well, we are trying to get Wayland into Archlinux and Weston package can use Cairo's EGL backend along with either GL or GLESv2. If Wayland (the library) package gets accepted, I'll send patches for MesaLib and a PKGBUILD for Weston, too so Archlinux will bring users newest software.

You may think that neither Wayland or Cairo GL backend are usable, but they are. As for Wayland, protocol is marked stable and if someone would like to develop app that works on Wayland, he/she would have to install everything from source on Archlinux instead of just installing it on the fly.

Cairo GL is, indeed, marked experimental, but it does not harm any apps that don't use GL backend functions. I have sucessfully verified and confirmed that Cairo built with GL support will work with proprietary libGL's such as ones from nVidia or AMD proprietary drivers.

I am attaching a patch for Cairo's pkgbuild in order to enable gl and egl backends together.

Regards.