Without this Divinity: Original Sin Enhanced Edition crashes at start-up. Technically this is a game bug as it does have a path for drivers without this extension but it detects the extension in a buggy way.
Lets stop punishing our users and just implement this extension.
The extension is fairly self contained so it shouldn't really place much burden on us maintenance wise.
Mesa bug report: https://bugs.freedesktop.org/show_bug.cgi?id=93551
Piglit tests: piglit!111 (merged)