[cairo] SVG backend

[Emmanuel Pacaud]

Hi,

I've just finished the port of SVG backend to use paginated surface API.

As a result, SVG backend is now able to produce SVG 1.1 files by using
image fallbacks for other operator than OVER. There's an optimisation in
paint method that avoid to trigger image fallbacks when using CLEAR and
SOURCE operators and when there's no active clipping path.

The ability to produce SVG 1.2 and to use "comp-op" element is still
there, but we need to define an API for selecting SVG version.

A side effect of this port to paginated surface is it magically provides
an implementation of acquire_source_image method.

My patches sit there:

http://gitweb.freedesktop.org/?p=users-emmanuel-cairo;a=shortlog;h=analysis-surface

I've not pushed this work to master, since it needs a review of
modifications made to ps, pdf, paginated and meta surfaces.

Regarding testsuite, 12 tests fail:

	- 7 because of 1 digit error on colors.
	- 4 because of a 0.5 pixel shift of composited images.
	- the last one being rectangle-rounding-error.

4 tests trig image fallbacks, which are operator tests.

	Emmanuel.