[cairo] new pattern interface patches and some great news about the OpenGL backend

[Carl Worth]

On Apr 1, Carl Worth wrote:
 > Finally, after applying this patch I am getting some segfaults in xsvg
 > with an unpatched libsvg-cairo. I'm looking into that now, and if it's
 > it the new code I'd like to fix it before we commit.

Whoops.

Of course that won't work since the type signature of
cairo_set_pattern has changed.

Which reminds me, the pattern patch should also bump the cairo version
so that libsvg-cairo can be made to require the new version.

So now, with the libsvg-cairo patch applied I'm not seeing any
segfaults. There are some nice improvements, (radial gradients, linear
gradients on stroked text), but there are some regressions with linear
gradients as well. Most of the regressions are minor, and it may be
that most of the bugs are in libsvg-cairo, not cairo itself.

So, if you address the points in my previous mail, I don't see a
reason not to commit the pattern patch.

-Carl