cairo: disable trace and trace interpreter

The Cairo tracing and trace interpreter are most likely not that
useful, so disable them. They also require zlib, which isn't a
dependency of Cairo at the moment. This fixes the following build
failure:

  http://autobuild.buildroot.org/results/a91e4e337fd9deb0f9fad433350feb27b2aee556/build-end.log



In the future, if people are interested by the trace and trace
interpreter, we can add a new Config.in knob for them.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>