Now that the OpenGL driver package is named "opengl", we can finally get rid of the ugly "glimpl" name. Signed-off-by: Elias Naur <mail@eliasnaur.com>
There are no longer any importers of package backend outside of gioui.org/gpu. Move it internally, and rename it to the slightly more specific "driver" while we're at it. Signed-off-by: Elias Naur <mail@eliasnaur.com>