improve Cairo test
improve Cairo test

- check against runtime cairo version, not compile-time
- limit tests to Cairo 1.8 as 1.9 changed rendering output slightly
  which makes tests fail

mltframework/swfdec,freedesktop-unofficial-mirror/swfdec__swfdec,mltframework/swfdec,freedesktop-unofficial-mirror/swfdec__swfdec,freedesktop-unofficial-mirror/swfdec__swfdec