[Mesa3d-dev] dri-extension branch - clean up advertising extensions in Gallium

[Marek O. <ma...@gm...>]

This branch is aimed to address the following issues:
* Extensions are advertised in both st/mesa and st/dri, doing the same thing
in two places.
* The inability to disable extensions in pipe_screen::get_param because
st/dri overrides the decisions of st/mesa.

Here's the branch:
http://cgit.freedesktop.org/~mareko/mesa/log/?h=dri-extensions

The first commit moves the differences between st/dri and st/mesa to the
latter and removes dri_init_extensions from st/dri. It doesn't remove any
extensions from the list except for those not advertised by pipe_screen.

The second commit enables texture_rectangle by default in Gallium. To my
knowledge any Gallium hardware can do this and I suspect it was dependent on
NPOT textures by accident.

All this is of course tested with piglit and glean.

Please review. In case it's not OK, please let me know what needs to be
done.

-Marek