[cairo] Updating cairo-demo/qcairo to current API

[Mauricio Piacentini]

> <svg.h> is from libsvg, <svg-cairo.h> from libsvg-cairo, and both can be
> found in the :pserver:anoncvs at cvs.cairographics.org:/cvs/cairo CVS.
> There should probably be a configure check for this ...

I think there is, at least in the cairo-demo/sdl example. But in my case 
I built and installed both (libsvg and libsvg-cairo). The demo builds 
correctly, but when it runs it only displays a white screen. What does 
it do on your system?

Regards,
Mauricio