[cairo] Any objections to dropping _cairo_atsui_font_old_show_glyphs?

[Baz]

Just looking for comment on this. _cairo_atsui_font_old_show_glyphs
was used to display glyphs under the old quartz code, for all
surfaces. More recently its become unnecessary for any surface and in
fact only gets used in these (rare) circumstances:

- atsui text is being rendered to a quartz surface
- and we cannot render the text in cairo-quartz-surface (this happens
because, eg we cannot convert a pattern to a CGShadingRef);
- and we can extract a destination image surface from the quartz
surface. The code looks like the original quartz surface could be
used, but this is actually unreachable.
- and we can create a CGBitmapContext matching the destination image
surface. This should always succeed.

If any of that fails it ends up using glyph surfaces, which should
work anyway - they are used for all non-quartz surfaces.

Does anyone see this code[1] getting used in the real world? It isn't
being hit by any of the tests any more, but of course its still just
as buggy as it was with the old quartz :). If no-one is actually using
it, I think we'd be better off without.

The cut would just be 150 lines or so. Some of this comes from
inlining what little of of cairo-atsui's
CGBitmapContextCreateWithCairoImageSurface is still required.

Cheers,
Baz