ae0cfe80c4
This option is based on a recommendation from a page last updated in 2014 (see https://www.freedesktop.org/wiki/Software/Glamor/), and it is not necessary anymore. Also, it did the wrong thing: it forced DRI2, but Glamor should also work with DRI3, that is a better option most of the time. So let's remove this option, folks that still want to force this manually can do so in other ways.